[editor] Fix duplicate map meta entries resulting in editor suspending.

[chris1384]

Fixes #538

This does not check for multiple files with different attributes (ex. scripts type that use both client and server instead of shared).

[jlillis]

I'm not sure ignoring duplicate entries is the best idea - there should a warning shown to the user informing them of the issue. If editor is duplicating files that means there is a bug that needs to be fixed.

[chris1384]

The editor does exactly what the map meta contains, but it fails at fileCopy if there's a file already copied.
I wouldn't say that the editor is at fault here, it's either the users fault or an another resource with general.ModifyOtherObjects permissions and writes extra lines in the meta. I can't think of a better approach for this so feel free to suggest anything. :d

[jlillis]

I wouldn't say that the editor is at fault here, it's either the users fault or an another resource with general.ModifyOtherObjects permissions and writes extra lines in the meta.

I think you're probably right. If this breaks anything at least we'll have a debug warning to trace it with.