Summary:
1. Provide forceRTL function for developer to test RTL layout in LTR language bundle in I18nUtil and expose it in I18nManager.
2. Rename `allowRTL` and `setAllowRTL` functions
Reviewed By: fkgozali
Differential Revision: D3663693
fbshipit-source-id: 3db13a44c069ae73d1728c211306422db5dd8122
Summary: Rename the forceRTL to allowRTL so that make it much clear to read. And change a typo.
Reviewed By: fkgozali
Differential Revision: D3489235
fbshipit-source-id: b9803dfbcda2f764b7e752c9810cfc7a0b9fe39b
Summary: Create a module for React Native to get IsRTL information and set ForceRTL function.
Reviewed By: fkgozali
Differential Revision: D3446871
fbshipit-source-id: 736edf138a89d222818071370ac49dc54bda63b7
Mengjue Wang