Use `cocoapods` as CLAide#Command.plugin_prefix

To create a CocoaPods subcommand plugin gem, add the file
`lib/cocoapods_plugin.rb` and load your subcommand implementation from there.

When the `pod` command runs, it will look for that file in your gem and load
it before parsing the command line.

Corrected wrong output path passed to actool for Apps.

[CHANGELOG] CLAide plugins enhancement

Avoid compiling xcassets in some cases

Added a condition to avoid compiling xcassets when WRAPPER_EXTENSION
is undefined, as it would be in the case of static libraries. This prevents
trying to copy the compiled files to a directory that does not exist.

[rake] Temp disable spec run on release, because locally Xcode is failing the examples at the ‘install’ phase.

Fixes #1503

separated spec:unit from spec:unit_quiet