Clean up the association subtheme

Now that we moved the linnovate branch changes upstream for the base theme (see #786392: Push bluecheese changes upstream), let's clean up the association subtheme from anything that cannot be implemented in a more portable manner. Attached is a diff of the changes between that and the base theme.

Looks like it boils down to a few things:

- a hardwired mission, which we agreed on at #791904: Subsite home page headers should be standard height that it should not even be there
- addition of page title tools even on the front page(?!)
- general.js changed for search title, we maybe should move this to a site specific JS file?
- content nav links added from primary links
- header nav building from crossite module (but difference of these to crossite module was all ported to crossite module already and is available on the DRUPA-6--1 branch of that module, see screenshot in #786392: Push bluecheese changes upstream)
- footer link building ditto
- masthead link building ditto
- a new section name variable, what's that for?
- links list building with custom code, uses HTML concatenation while parent theme used arrays
- the rest is once again lots of code copied from crossite module

As I've said in #786392: Push bluecheese changes upstream, we can drop all the crossite module copied code, check out a DRUPAL-6--1 branch copy of drupalorg module, enable the crossite module and set $conf['drupalorg_site'] = 'association'; in settings.php, and it will work the same I believe. I tried to ensure in my recent updates to the crossite module that all the association theme changes are in there. I can demonstrate it working on the live localize.drupal.org to whoever wants to see it (even though the internals of the site will not look right due to CSS issues specific to that site which still need to be solved). Just tell me your l.d.o user URLs if you are in doubt and I can empower you :)