CB-7220 Split cordova help into per feature help files

This splits the documentation for the various commands into individual files.

It also exposes the bash help (although it doesn't mention that it's there).

It also documents the breaking change introduced by https://issues.apache.org/jira/browse/CB-6024 to cordova run's argument parsing.

The second commit enables downstream users to cordova-cli to share cordova-cli's help w/o having to reinvent it.