uix:ActionBar make items added to ActionOverflow persistant in the
overflow dropdown. Minor bug fixes.
uix:Settings fix handeling of numeric input, no body had a issue with
this??
uix:ActionBar fix group_index to be calculated after all groups have
been added
uix:ActionBar allow changing of proeprties like color, mipmap, border
through the ActionItem.
uix:TabbedPanel introduce new `strip_image` and `strip_border`
properties that can be used to easily  customize Tab strip.
New german QWERTZ keyboard layout
simultaneous system and virtual keyboard input
Merge branch 'master' of https://github.com/kivy/kivy into dual-keyboard-mode
Merge pull request #1404 from rentouch/dual-keyboard-mode

Dual keyboard mode & New german keyboard
config: add versionchanged for systemanddock and systemandmulti values to keyboard_mode
Merge pull request #1402 from kivy/tabbed_panel_strip

uix:TabbedPanel introduce new `strip_image` and `strip_border`
Merge pull request #1399 from kivy/action_overflow

uix:ActionBar make items added to ActionOverflow persistant in the overflow dropdown. Minor bug fixes.
Merge pull request #1398 from kivy/numeric_settings

uix:Settings fix handeling of numeric input
core: fix remaining basestring left in the code
Merge branch 'master' of ssh://github.com/kivy/kivy
Merge pull request #1403 from eulerreich/lang_handler_memory_leak_fix

Solved issue #1388 where ``lang._handlers`` keeps widgets alive.
lang: remove whitespace and unused modules
Merge branch 'master' of ssh://github.com/kivy/kivy
Further fix for ``lang._handlers`` memory leak related to ``Bubble``.

Original problem: Bubble constructs BubbleContent before finishing its
own construction, thus never initializing its ``_proxy_ref``, causing
``lang.get_proxy`` to return the Bubble itself (this is when creating
handler for BubbleContent's color from parent color). This in turn
caused ``lang._handlers`` to unnecessarily keep it alive. 

The fix: I let ``Widget._proxy_ref`` be generated lazily on demand
instead of relying on ``Widget.__init__``: whenever the user calls
``Widget.proxy_ref`` for the first time, ``Widget._proxy_ref`` will be
initialized. I don't see any particular reason to initialize
``_proxy_ref`` only in the ``__init__`.
Merge remote-tracking branch 'kivy/master' into lang_handler_memory_leak_fix