Bug 775542: Prevent templates from overriding with default langfiles.

The base templates had specified "main" in a "set_lang_files"
tag. This was causing child templates to look in "main.lang"
before the lang file for the template. This removes those
errant calls, as well as prevents such accidental additions
from breaking things in future.
Merge pull request #634 from pmclanahan/bug-775542-exclude-defaults-from-langfiles

Bug 775542: Prevent templates from overriding with default langfiles.