GCS cleanups

[Yavor Doganov]

Regarding these two TODO items:

| *** Standardize all variables'/rules' names.

I suggest to get rid of the underscore in variables that are not
ALL_CAPS, and replace it with a dash.  It is easier to type, more
natural for make and indeed the recommended way.  So home_rules will
become home-rules, template_files -> template-files, etc.  We have
been using the word-word(-word) convention for some time anyway.

This is also a good opportunity to unify/rename all variables that beg
for renaming -- confusing or inconsistent names and other things.

Also, as previously discussed, let's get rid of these
LITTLE-CUSTOM-TOOL variables; their usefulness is rather questionable.

| *** Wrap long lines where possible.

This is self-explanatory.