Files: prevent people from renaming files to '.'
rename containsInvalidCharacters() to isFileNameValid() - NOTE: semantic has changed!
adding file name checks and notifications to isFileNameValid() for . and empty file name
Merge pull request #1092 from owncloud/rename_dot

Files: prevent people from renaming files to '.'
Merge branch 'master' into fixing-998-master

Conflicts:
	apps/files/js/files.js