Force Fetch should ignore file extensions and not error out

[jimpdx]

It would be nice if force fetch could ignore the file extension and not fail if you happen to still include .flow or .cls or whatever metadata file extension is used.

$ force fetch -t Flow -n New_Financial.flow 
Entity of type 'Flow' named 'New_Financial.flow' cannot be found

$ force fetch -t Flow -n New_Financial (OK)

[cwarden]

As of #657, force fetch can be used with paths, so either force fetch -t Flow -n New_Financial or force fetch src/flows/New_Financial.flow can be used.