Check mixed case version files

[HebaruSan]

Problem

Two mods have vrefs and version files with non-lowercase file name extensions:

They're not being picked up.

Cause

The search for .version files is case sensitive.

Changes

• Now the search for .version files is case insensitive, so these version files will be found
  • Both of them have severe syntax errors, so we'll need to remove the vrefs to inflate them, but that's better than having vrefs with version files that get silently ignored
• Regexes for checking file extensions are replaced with string.EndsWith calls, which ought to be faster given the complexities of each operation (the runtime can jump to the common parts based on the string lengths and compare character by character, rather than building and running a finite state machine and feeding in the entire string character by character until it reaches the end)
• The Regex for checking the vref-configurable AVC path is now compiled and only generated once, which again should be slightly better for performance

[DasSkelett]

Looks good