Jetpack: Make the module list filterable

[dllh]

It'd be neat, especially for multisite installs, if Jetpack modules could be turned off by a plugin. I chatted briefly with George Stephanis, who agreed (I think) that filtering the list of plugins vs. just blindly iterating over php files and including them all might be useful. I hereby make the request.

[dllh]

Adds a filter for suppressing modules

[dllh]

I've attached a patch that seems to do the trick.

[jeherve]

Fixed in r759391 - Add in a jetpack_get_available_modules filter to let plugins or site admins blacklist Jetpack modules.

props georgestephanis