Local Dev version of manifest file

[npalladium]

Currently, when we reload the extension from a local repo we are developing from, it replaces the installed extension.

I'm thinking we could do something like: locally, the manifest file will have a different name for extension but git will store the correct name too. We can exploit git's features for this.

[npalladium]

@AdaephonBen, @TarunNoone what do you think?