Update Og's context to use the menu system

well, this issue encouraged me to dive into the whole OG's context. Here's what the patch does:

1) Use the menu system to find the context.
2) Reorganize code, for example - move away from og_set_theme() the part that gets the $group_node.

I haven't tested the Views AJAX and I have one thing I didn't understand what it's supposed to do - what is this menu path?!:

  elseif (arg(0, $path) == 'node' && arg(1, $path) == 'add' && arg(2, $path) == 'book' && arg(3, $path) == 'parent') {
    $group_node = og_set_theme(arg(4, $path));
    $_REQUEST['edit']['og_groups'][] = $group_node->nid; // checks the right box on node form
  }

As for the original patch, I think maybe the way to do it is having a service to og_set_conext() - I'll create a different issue for it.

I've started with using menu_get_object() however it served me only on node view/edit (The comment for example doesn't load) so in the end I thought I'd better just use menu_get_item() for consistency.

actually, I'll re-roll. menu_get_object() even for the node view/ edit is cleaner.

Ok, late at night, so I hope there aren't too many errors...

Changes from last patch:
1) Use menu_get_object() for existing nodes.
2) og_form_alter() is trying to be more friendly, which means it checks if the user clicked the 'Preview' button and a group was selected; Or if the user has a single group and audience is required.
3) simpleTest :)

Some more changes:

* form_alter() tries to set the context only if no context was already set - like this we don't override other modules set_context().
* I've removed the views_ajax() part. We should find another solution rather than relying on the menu system, since the path is 'views/ajax' and unfortunately menu_get_object() returns nothing. maybe we can use hook_view_pre_render(), but I think this can be done in a following patch.

Some more fine tuning on the OG context selection 1 + 4 added:

+ // Group post belongs to multiple groups. Selection order:
+ // 1) URL has gids[] and user is a group member.
+ // 2) The group we showed on the prior page view (if any).
+ // 3) The only or one of the group(s) the current user is a member of.
+ // 4) The first group, if the user has 'administer organic groups'

hmm, I found a better way to do this, will re-roll soon.

Ok, now if user passes ?gids[]=X, system checks user is a member or 'administer organic groups'.

For a path like og/manage/%node, you can use menu_get_object('node', 2).

Done.

Oops, wrong patch :/, sorry.

Re-rolled.

And again.

Working on Mosh'es comments from the IRC, and make sure the test pass.

og_set_group_context() now doesn't try to determine itself the group node.
All tests pass.

I've kept only the 'menu system' part and addressed your comments.

One day I will get it done correctly right on the first patch ;)