use new (as in Django 1.3) url tag which will be the default in Django 1.5

This kills a lot of DeprecationWarnings when running the testsuite with -Wall
use the new _mptt_meta object instead of _meta to access tree attribute names

this gets rid of some warnings both in the test suite and when running live sites
turn children qs into list

this brings us compatibility with django-mptt 0.5.2
updated the docs to indicate that we now require django-mptt 0.5.2

also updated the django-sekizai version in the docs
Fixed import which caused error in cookie unquoting
Added Aleš to AUTHORS
laxed the required mptt version a bit, we now support >=0.5.1, <0.6
Convert up/down arrows in menu item to unicode character (as for the oblique arrow). Fixes #1305
Added a bit of padding aroung icons in menu_item.html
Arrow padding in item list is now done via css. Moved border definition to 'HTML style' to css
pumped up font-size of arrows a bit and removed text-decoration on hover
added note about mptt in upgrade docs
Merge pull request #1313 from piquadrat/feature/mptt-0.5.2-compat

compatibility with django-mptt 0.5.2
Merge pull request #1301 from evildmp/YAMD

multilingual docs added to concepts section
bumped version to 2.3rc2 and added a note about mptt version in CHANGELOG
Merge branch 'release/2.3rc2'
Merge branch 'release/2.3rc2' into develop
bumped version to 2.3rc2.post0
Add 'last' class to items in lazy_child_menu.html
Reworked patch to use forloop variables