Move all etc/upgrade scrips to .in files, and standardize their init

Fixes: I#18856
Add policy tests for etc/upgrade/ files
\Q and \E only affect within their given string

Splitting the \Q and \E into differing double-quoted strings has no
effect -- and as $domain is not substituted into either of them, it does
not gain the beneficial effects.  That is, if $domain is "example.com"
the generated string will contain "(?:foo|bar)\@example.com" without the
"." escaped.

Embed the $domain substitution between the \Q and \E so it is effective.
This was detected by a warning found in the previous commit.
Make sure the non-.in bin/ and sbin/ files are +x
There is no reason for config, acl, schema, and initialdata to be +x
There is no reason for doc files to be +x
These top-level files need not be +x
Prepend default install location to all command-line scripts

Explicitly include the default installation path to all commands in
documenataion.  Many of these lacked them because previous to efaf506b,
etc/upgrade/ was not installed.
Replace hardcoded paths with configure-time paths when possible

This also corrects an error in rt-email-dashboards, where the path to it
was mistakenly given as local/sbin/ instead of sbin/
Merge branch '4.2/upgrade-and-policy' into 4.2-trunk