CCSM: Recommendation function needed for various plugins

[MC Return]

Problem:

A lot of plugins are dependend on other plugins for full functionality.
A good example for this are the plugins, which need the text plugin to
fully work.
(scaleaddon, stackswitch, shift, scalefilter, thumbnail, ring)
This text plugin dependency is not essential for those plugins to work,
but without the text plugin being activated, they won't render any text.
The user won't ever be informed about that fact though.

Solution:

Implement a <recommendation> .xml keyword that is used to inform the user,
that a plugin is recommended by another plugin and allows him to select
if he wants to follow this recommendation or not.

Note:

Currently we have the <feature> and <requirement> keywords, which
will be detected by CCSM, but there is no way to have a soft dependency.