Also put "Improve handling of app extensions…" back into enhancements, where I moved it during the PR

[Installer] Print message when skipping user project integration

Fix shellscript in '📦 Check Pods Manifest.lock'

Require active_support in xcconfig_helper

This ensures that scripts like xcpretty can differentiate default output
and error output.

The script is integrated using /bin/sh but [[ is not defined in generic
POSIX shell. Confirm shellcheck error:

if [[ $? != 0 ]] ; then
   ^-- SC2039: In POSIX sh, [[ ]] is undefined.

This works right now, because on common OS X systems, /bin/sh is Bash.
But this might change in the future.

[Installer] Use user defined swift version

Improve handling of app and watch os 1 extensions

[Installer] Verify no duplicate static libs

Fix code signing in Xcode 8

This sets `CODE_SIGN_IDENTITY` to empty for all generated aggregate and
Pod targets.

[repo/push] allow URLs for pushing to private repos

Set 'Allow app extension API only' for Messages extensions

[repo/push] --use-json to convert podspecs to JSON format when pushing

- More app extension -> embedded target