This function deletes files from the source control system.
The source control plug-in implementation of this function is expected to return one of the following values:
Removal was successful.
The selected file is not under source control.
The source control system does not support this operation.
Cannot remove a file because a user currently has it checked out.
There was a problem accessing the source control system, probably due to network or contention issues.
The user is not allowed to perform this operation.
Nonspecific failure; file was not removed.
The operation was cancelled before completion.