General project refactor

[piranna]

This pull-request acomplish several things:

• Checked and ensured re-base template generates a project that works untouched on Android, web and Electron (should work on iOS, but I can't be able to test it)
• Removed useless or duplicated files from re-base template to make it as minimal and out-of-the-way as possible
• Fixed templates placeholders so project name gets correctly filled everywhere
• Added build scripts for all platforms to package.json, so there's no need to learn external tools, everything can be build with npm run <platform> and npm run <platform>:release.
• Layered architecture so several templates can be applied ones on top of anothers to customize the scheleton created by re-base template (still untested, but should work)

[piranna]

Ok, so thanks to a current client interested on re-start, I've have time to review the refactor and finish it. The latest changes that I've done has been removal of setting devDepedencies since React Native CLI now has support for it, updated to Electron 4, and more important, I've been able to test and fix the layered templates, so now they are working correctly and we can start to create templates adjusted to our own needs. I could be able to merge it in master branch a version 0.4 but I don't have permissions to publish it on npm, so @amoghbanta, could you be able to take a look at the pull-request and publish it on npm? :-) By the moment they are published by myself as re-base_piranna and re-dux_piranna, but i would like to have it merged upstream...