CM File Manager - Gracefully handle renaming on case-insensitive filesystems

Add edge case handling to move/copy commands wherein something is being
renamed to a different-cased version of itself.

Ex : renaming 'mydocuments' to 'MyDocuments'

https://jira.cyanogenmod.org/browse/BACON-3074

Change-Id: Id90de5fd083e341371f250c0194f200388cf4941