Add compiler warning about CS file name not matching the class/interface contained within

[ericwood8]

Summary

Add compiler warning about CS file name not matching the class/interface contained within. Maybe wording could be "File Name/Class Name mismatch."?

Background and Motivation

Help produce cleaner code

User Impact

None, except for seeing warning on build.

Which Files?
Skip:
CS files with multiple classes
non-class & non-interface CS files
non-CS files such as *.html

Include:
CS files with interface

Implementation

Would delay building/rebuilding but can minimize impact of checking. Maybe cache a integer (0=no known mismatches, 1=known mismatches, 2=unknown state) that there are problems or not. If problems, then keep checking on subsequent compiles. If no problems with file/class name mismatches, then no need to check on subsequent build/rebuilds. If freshly starting VS, then start with unknown state. If load a new solution into VS, then reset the cache to an unknown state.