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
Fixed a logic error inlazy menu queryset checks and minor optimizations (thanks to @piquadrat for pointing this out)
Use {% with %} as a further optimization