[BUG #4831] Refactoring: Resolution independent CSS

* ToggleButton has no possibility to adjust its label size via JS. It used text ellipsis instead when state labels are too long.
[BUG #4831] Refactoring: Resolution independent CSS

* Extracted 2 new SCSS files "input" and "scroll" for global InputFields and ScrollComposite.
Minor update of qx.Mobile Toolbar Showcase.
[BUG #4831] Refactoring: Resolution independent CSS

* Removed qx.bom.AnimationFrame on updateSlot because it caused a bug.
[BUG #4831] Refactoring: Resolution independent CSS

* Added "_gradients.scss" which contains functions and mixins for creating cross-browser linear and radial gradients.
* Removed iOS6 SCSS files.
* Removed Android 2 SCSS files.
Reset iOS and Android css files to qx version 3.0
Merge "theme" SCSS into specific widget SCSS files of basic folder.
[BUG #4831] Refactoring: Resolution independent CSS

* Changed SCSS parts loading order.
[BUG #4831] Refactoring: Resolution independent CSS

* Added pxToEm function which enables the user to scale the application through root font size ($application-font-size as variable)
[BUG #7244] refine drag drop scolling mixin (and add table support)
[BUG #7244] add drag & drop for virtual list demo
[BUG #7244] add drag scrolling mixin to AbstractScrollArea and Table
[BUG #7244] replace hard dependency with duck typing
minor
[BUG #7708] refac: renamed lint.extension_match_in to global_symbols.test_for_libsymbol
[BUG #7708] some code cleanup

- also using the new class boundary pattern, (?=\.|$)
[BUG #7708] some code refac in unknown_globals()
[BUG #7708] replaced _splitQxClass with test_for_libsymbol

- in MClassDependencies.depsItem_from_node