Filter features diff in drush by component

Yes indeed.

I notice some consistency issues, though:

• Looking at some other drush commands' arguments (l10n_update, generate-makefile) I noticed they do comma separated lists of stuff in their arguments, not space separated.
• Other drush features commands refer to 'components' as "Component types", "Components" are the individual items inside the components. To prevent confusion to the drush user, we should unify this.

So I changed a header too. (Since the code outside features.drush.inc usually uses '$component' as a "Component type", I didn't change variables.)

Oh yeah, and I moved the processing of the argument more to the top (splitting one patch hunk into two) on purpose, because I need $filter_ctypes for my next patch :)

...and if someone likes this, they might also like #2052579: Speed up features diff for selected components..

(That issue is 'needs work' because that patch fails to apply until this issue is incorporated.)

I think "ctypes" needs to be changed to something like "components" to make it more consistent with other drush command arguments/options?

I think not.

What drush commands refer to "components" are the individual items. Like 'views_view.VIEW_NAME'.

Our diff command cannot do this, but can only select the 'groups' of these components. Like 'views_view'.

IMHO if we refer to our selections as "components", we create confusion, by naming 2 different things "components". This is explicitly why I didn't name things "components", but chose 'ctypes' instead. 'component-types' would also do, if you like that long a commandline argument...

Reroll against RC3.

Committed to ac15c4e.