Embed frameworks into app and watch extensions.

[Validator] Add private mode

[TargetIntegrator] Remove embed frameworks build phase where not needed

Create an own method #remove_embed_frameworks_script_phase which takes a native target and returns whether modification were made.

Fix watchOS Example Podfile referencing non-existent branch

[Validator] Print the name of the attribute that has the result

[CONTRIBUTING] Minor improvements

Fixes #3546

Collapse public and private pod xcconfig into one

Fixes #3906.

[Copy] Framework support is out of beta

Changed the default template Podspec description to be a comment.

[Installer] Add support for source provider plugin hook