Improve changing bundler support
Improve changing bundler support

Summary: This makes it so that you don't have to specify the package to the bundle. When you don't specify it, it will use the default bundle that is chosen when the app starts.

Reviewed By: PeteTheHeat

Differential Revision: D15742001

fbshipit-source-id: cd5906a66d04eea308dbc0516bc1fec60caed6bb

exponent/react-native,pandiaraj44/react-native,hoangpham95/react-native,hoangpham95/react-native,myntra/react-native,javache/react-native,exponent/react-native,facebook/react-native,hammerandchisel/react-native,hammerandchisel/react-native,janicduplessis/react-native,hoangpham95/react-native,exponentjs/react-native,exponent/react-native,exponentjs/react-native,hammerandchisel/react-native,myntra/react-native,exponentjs/react-native,javache/react-native,arthuralee/react-native,hammerandchisel/react-native,facebook/react-native,exponent/react-native,pandiaraj44/react-native,javache/react-native,facebook/react-native,exponent/react-native,pandiaraj44/react-native,facebook/react-native,myntra/react-native,janicduplessis/react-native,exponent/react-native,pandiaraj44/react-native,hoangpham95/react-native,exponentjs/react-native,facebook/react-native,janicduplessis/react-native,hoangpham95/react-native,javache/react-native,hoangpham95/react-native,arthuralee/react-native,javache/react-native,facebook/react-native,hammerandchisel/react-native,exponentjs/react-native,facebook/react-native,janicduplessis/react-native,exponentjs/react-native,exponent/react-native,arthuralee/react-native,pandiaraj44/react-native,facebook/react-native,hoangpham95/react-native,hammerandchisel/react-native,hammerandchisel/react-native,janicduplessis/react-native,pandiaraj44/react-native,janicduplessis/react-native,javache/react-native,janicduplessis/react-native,facebook/react-native,arthuralee/react-native,myntra/react-native,myntra/react-native,janicduplessis/react-native,javache/react-native,myntra/react-native,hammerandchisel/react-native,exponent/react-native,exponentjs/react-native,javache/react-native,myntra/react-native,myntra/react-native,myntra/react-native,exponentjs/react-native,javache/react-native,pandiaraj44/react-native,hoangpham95/react-native,pandiaraj44/react-native,arthuralee/react-native