Add .tpp header support

Sync main master with czechboy0 master

Migrate local Ruby podspecs to JSON

What 1eb3584a should have been

[PathSource] Remove the stored lockfile checkout source when switching t...

[Installer] Automatically detect conflicts between framework names.

[Init] Output a properly-formed `Podfile` when running `pod init` with a target that contains a `'` in its name.

Closes https://github.com/CocoaPods/CocoaPods/issues/3136.

Closes https://github.com/CocoaPods/CocoaPods/issues/2983.

Build for iOS simulator only during validation

[Outdated] Update podfile sources

Update embed_frameworks_script.rb

Fixed symlink framework issue caused by spaces in `source`

Refs https://github.com/CocoaPods/CocoaPods/issues/3108.

Installation of app-extension targets which had no dependencies
configured in the Podfile would cause an exception before.

Fixes CocoaPods/swift#13