Add tag generation for the module code

Adds ctag support for chapel via the --regex and --lang[def|map] options
and uses it to generate tag files for our module code. `ctags -e` is now
used to generate the emacs format for compatibility with these options.

Also consolidated a few rules in the .gitignore for tag files, we now
generally ignore any tags or TAGS file.
Remove type declarations from Chapel tags

While it might be nice to have type declarations in the tags, we tend
to use them as variables in quite a few places and this leads to many
duplicate tags.
Add a new chpltags utility

chpltags wraps both Exuberant Ctags and etags, allowing for the creation
of both emacs and vi compatible tag files for Chapel code. This new
script is now being used to create the tag file for the modules. The
ctags.chapel file that was being used previously has been removed
Improve the chpltags help message

Improved the chpltags help message based on feedback from
@thomasvandoren.

Added a check to ensure that a ctags executable can be found before
calling it.
Move chpltags into the util/ directory

chpltags is now in the root util/ directory and has been added to the
release.
Merge pull request #925 from Kyle-B/kb-add-chapel-ctags

Add tag generation for the module code

Adds ctags support for chapel via a new utility script, `chpltags`. `chpltags`
uses the regex options supplied by ctags and etags.

`ctags -e` is now used to generate the emacs format for compatibility
with these options if possible, otherwise etags is used.

Also consolidated a few rules in the .gitignore for tag files, we now
generally ignore any tags or TAGS file.