module_disable() functions, and utilize them when enabling
and disabling modules to notify the user of dependent and/or required
modules that are being disabled/enabled in addition to the named
modules.

Issue backdrop-contrib#164

- Pull temporary code into its own file includes/dependencies.inc
- Make use of bee_instant_message() where appropriate
- Add clarity to user message when a dependency of a dependency is disabled
- Fix code comment typo abled() -> enabled()
- Updated changelog

Issue backdrop-contrib#164