Assuming relative paths in ShowHistory breaks Approvals history display

Show Outgoing Email goes to /Approvals/ShowEmailRecord.html which
doesn't exist.  Additionally, Reply/Comment/Forward are broken (although
shouldn't be visible, fixed in a later commit).

This also shows up in RTIR where links point to
/RTIR/ShowEmailRecord.html and /RTIR/Attachments/

Fixes issues 29800 and lays groundwork for a fix in RTIR for 29775.

While you could list /Ticket/Update.html and /Ticket/Crypt.html for the
6 *Path variables passed in %ARGS, it's nicer if you can just say "use
everything from /Ticket/, like you used to in 4.0".

Broken when moving to relative-by-default paths in 8274e2b6.

Since /Elements/ShowHistory isn't directly callable and the JS helper doesn't
pass extra arguments, there are currently no ways to pass a malicious
PathPrefix in from user supplied data.
In 4.0, ShowTitleBarCommands didn't hide Outgoing Email links

The 4.2 equivalent ShowActions should be compatible for the places
that want to suppress Reply/Comment/Forward.

This makes the code change, leaves whitespace terrible.
Whitespace only change

The previous commit removed an outer if block and pushed it into the
boolean check of the elsif, leaving it weirdly indented.  This left
shifts everything as a separate commit to make reading the previous code
change clearer.
Switch to ShowActions from ShowTitleBarCommands

f0137c97 deleted ShowTitleBarCommands but commits which were merged
later (0d8eacf3 and 775f4bd1) used them for newly refactored code,
causing Reply/Comment/Forward to pop up all over the Approvals display,
and generating links that either loop back to the approvals page or
otherwise don't work.
Merge branch '4.2/showhistory-paths-and-titlebars' into 4.2-trunk