Add version info into the apps (#330)

Both worker and coordinator display version number in the console during startup. Coordinator displays its version number in the top right corner of the index.html page.

scripts/version.sh

@@ -0,0 +1,30 @@
+#!/bin/sh
+
+file="$1"
+version="$2"
+from="(<span id=\"v\">).*?(<\/span>)"
+
+# Prints app version derived from git in the following format:
+#
+# v2-1-gcafeb
+# ^  ^ ^ ^
+# |  | | |
+# |  | | '- commit hash of HEAD (1st 5 symbols)
+# |  | '-- "g" stands for git
+# |  '---- n commits since the last tag
+# '------- last tag
+#
+# See: https://git-scm.com/docs/git-describe
+#
+# The first input param replaces the version placeholder in the provided file.
+# The second input param forces the use of some version value instead of a git-derived one.
+#
+if [ "$version" = "" ]; then
+  version=$(git describe --abbrev=5 --always --tags 2> /dev/null)
+fi
+if [ "$file" != "" ]; then
+  sed -i -E "s/$from/\1$version\2/" "$file"
+  echo "$file $version"
+else
+  echo "$version"
+fi