Disallow file and folder names that end with dots

Fixes:
#5468 (although I was never able to entire reproduce this case)
#7224 

This will allow for the user to create dots at the end of a file or directory name using the OS (finder/explorer) and Brackets will honor those but, because of the complexities of how the OS treats trailing dots in entity names, we disallow the user from creating entities that end with dots.

This is not for Sprint 39