That parameter was introduced in cbcc2fa5 and removed in d22b78c8

This way we do not loose the context of the current page. Further, the
new id generated from the query before wasn't really that useful (see
issue #1124 ). And we can still generate a meaningful link "create a
page for your query", if that is considered useful.

Further redirects exist for the old urls, so bookmarked searches etc.
should mostly keep working.

This adds two new config options:

`search_limit_to_first_ns`:
Limit the search to the current X namespaces. When a search is executed
from a page within a deeper namespace, the first X namespaces will be
added as filter.
Possible use case could be with language namespaces to ensure that the
default search is initially within the current language.

`search_default_fragment_behaviour`:
Option to specify the default fragment search behavior

This commit should be without functional changes.

during testing, redirects may not be executed, ActionAbort can default
to redirecting which ould create an infinite loop.

This was the last remaining function in inc/action.php that could be
moved to the actions.

We now have quite the elegant cascade in the action handling.

uses the explicit redirect abort on success

Action can now abort to 'redirect' to explicitly trigger a redirect
back to showing the current page. Automatic triggering for post->show is
now only done when a 'show' action was not explicitly requested.

This also removes duplicated code from ajax.php

loadAction() and checkAction() are now public and could be used within
actionOK(). However some weird circular references prevent that. In
addition, actionOK is also used to check for things that aren't Actions
(yet) like 'rss' and 'top'.

also fixes the tests

Now underscores can be used to have sub actions. The loader will try to
find an exact match first, then begin removing parts from the end until
a matching action is found.

This is not how integration of plugins would ideally be done in this new
system. Ideally an action plugin would actually implement an instance of
AbstractAction and would just fall into the normal flow of actions here.

However to not break a gazillion of existing plugins, this is just add
the existing two events into the new system through the use of a Plugin
action.

Maybe we could add "new" action plugins later.

Lots of FIXMEs and the routing isn't integrated, yet

This is neither complete nor working, yet