replaced the term "paste" with the more generic "document"

Some of the references to "paste" in code or comments got changed as well, but to clarify the intended usage of the terms:

- A PrivateBin document can consist of a paste text (key "paste" in the encrypted payload) and one or several attachments and discussion entries.
- Internally the root document is called a "Paste" and each discussion entry is called a "Discussion".
- When referring to a whole document with one paste and optional discussion(s), we call it just "document".
- When talking about a particular JSON payload type in the internal logic, i.e. during storage or transmission, we call them a paste or discussion to distinguish which type we refer to.

closes #397

cfg/conf.sample.php

@@ -39,7 +39,7 @@ defaultformatter = "plaintext"
 ; (optional) set a syntax highlighting theme, as found in css/prettify/
 ; syntaxhighlightingtheme = "sons-of-obsidian"
 
-; size limit per paste or comment in bytes, defaults to 10 Megabytes
+; size limit per document or comment in bytes, defaults to 10 Megabytes
 sizelimit = 10000000
 
 ; by default PrivateBin use "bootstrap5" template (tpl/bootstrap5.php).
@@ -79,17 +79,17 @@ languageselection = false
 ; if this is set and language selection is disabled, this will be the only language
 ; languagedefault = "en"
 
-; (optional) URL shortener address to offer after a new paste is created.
+; (optional) URL shortener address to offer after a new document is created.
 ; It is suggested to only use this with self-hosted shorteners as this will leak
-; the pastes encryption key.
+; the documents encryption key.
 ; urlshortener = "https://shortener.example.com/api?link="
 
-; (optional) Let users create a QR code for sharing the paste URL with one click.
-; It works both when a new paste is created and when you view a paste.
+; (optional) Let users create a QR code for sharing the document URL with one click.
+; It works both when a new document is created and when you view a document.
 ; qrcode = true
 
-; (optional) Let users send an email sharing the paste URL with one click.
-; It works both when a new paste is created and when you view a paste.
+; (optional) Let users send an email sharing the document URL with one click.
+; It works both when a new document is created and when you view a document.
 ; email = true
 
 ; (optional) IP based icons are a weak mechanism to detect if a comment was from
@@ -109,7 +109,7 @@ languageselection = false
 ; - If you use the bootstrap5 theme, you must change default-src to 'self' to
 ;   enable display of the svg icons
 ; - By default this disallows to load images from third-party servers, e.g. when
-;   they are embedded in pastes. If you wish to allow that, you can adjust the
+;   they are embedded in documents. If you wish to allow that, you can adjust the
 ;   policy here. See https://github.com/PrivateBin/PrivateBin/wiki/FAQ#why-does-not-it-load-embedded-images
 ;   for details.
 ; - The 'wasm-unsafe-eval' is used to enable webassembly support (used for zlib
@@ -131,7 +131,7 @@ languageselection = false
 ; See https://github.com/PrivateBin/PrivateBin/wiki/FAQ#why-does-it-show-me-an-error-about-an-insecure-connection for more information.
 ; httpwarning = true
 
-; Pick compression algorithm or disable it. Only applies to pastes/comments
+; Pick compression algorithm or disable it. Only applies to documents & comments
 ; created after changing the setting.
 ; Can be set to one these values: "none" / "zlib" (default).
 ; compression = "zlib"
@@ -172,9 +172,9 @@ limit = 10
 ; exempted = "1.2.3.4,10.10.10/24"
 
 ; (optional) If you want only some source IP addresses (v4 or v6) or subnets
-; (CIDR) to be allowed to create pastes, set these here. Invalid IPs will be
+; (CIDR) to be allowed to create documents, set these here. Invalid IPs will be
 ; ignored. If multiple values are to be exempted, the list needs to be comma
-; separated. Leave unset to allow anyone to create pastes.
+; separated. Leave unset to allow anyone to create documents.
 ; creators = "1.2.3.4,10.10.10/24"
 
 ; (optional) if your website runs behind a reverse proxy or load balancer,
@@ -182,12 +182,12 @@ limit = 10
 ; header = "X_FORWARDED_FOR"
 
 [purge]
-; minimum time limit between two purgings of expired pastes, it is only
-; triggered when pastes are created
-; Set this to 0 to run a purge every time a paste is created.
+; minimum time limit between two purgings of expired documents, it is only
+; checked when documents get created
+; Set this to 0 to run a purge every time a document is created.
 limit = 300
 
-; maximum amount of expired pastes to delete in one purge
+; maximum amount of expired documents to delete in one purge
 ; Set this to 0 to disable purging. Set it higher, if you are running a large
 ; site
 batchsize = 10