Move local-development mode to the separate plugin

[nikDemyankov]

As suggested in #17 - we need to move local-development mode to the separate plugin. This will make main plugin cleaner, and will add support for Xcode 6.4.

[nikDemyankov]

Moved to the separate plugin as an and add-on to this one. By default, all local-development stuff is removed from Hot Code Push plugin and moved to Hot Code Push Local Development Add-on plugin. Add-on is in the private repo right now, but will be published as soon as I'll finish with the docs. When you developing you project - just add it and see updates on-the-fly. As soon as you are ready for release - remove it, since you don't need it release version.