Merge pull request #297 from KaiVolland/extjs5

Port printextent-example to ExtJS 5.0.0
Merge pull request #298 from KaiVolland/extjs5

Fixed the test for PrintExtent
Rename bind and unbind functions in Slider classes

This renames the 'bind' and 'unbind' functions within the slider classes
of GeoExt because in ExtJS 5 it seems that 'bind' and 'unbind' are a kind
of reserved config properties (see
http://docs.sencha.com/extjs/5.0.1/#!/api/Ext.slider.Single-cfg-bind) so
our overwrite with a function enforces an exception in Ext.mixins.Bindable when
destroying a slider with its 'destroy' function.
Since 'bind' and 'unbind' were private functions a renaming seems
appropriate.
ZoomSlider and LayerOpacitySlider tests for ExtJS5

Adapted the tests for the Zoomslider and the LayerOpacitySlider to the new
mechanism so they are runnable either with ExtJS 4 or 5.
Merge pull request #301 from chrismayer/sliders-tests-ready-extjs5

Adapted tests for slider classes with ExtJS5
Merge branch 'extjs5' of https://github.com/geoext/geoext2 into extjs5
Port tree-example to ExtJS 5.0.1
Rename bind and unbind functions in LayerStore

see 3887196b47126440f3256fd26a182dd5232b337d
Adhere to stricter rules for itemId property

see 0214bbfd9fb6cd9711d24fc941c50dd0c7610aca
Cleaned constructor arguments
Add TODO wrt missing method afterEdit
Handle multiple records in remove-event.

see aaed903e69f0b36ebdd03c28beac5724768b4c16
Minor cleanups (Readability, Ext-Methods, ...)