Resolves #2790

- Also updated docs and examples for this
 - Fixed the positioning of the tooltip if groups was enabled
 - Removed missing parameters from Popup docstring

* Fix redraw order
* Fix error when option is not defined
* Allow template labels
* Fix boolean types bug
* Add subgroup stacking
* Almost finish subgroup stacking
* Play with examples for subgroup order
* Fix stacked subgroups
* Fix subgroup stacking
* Add stackSubgroups option
* Fix example
* Add docs
* Fix onRemove item subgroups recalculate
* Return subgroup example and add stackSubgroup example
* Split stackSubgroup example to subgroup/html and expectedVsActualTimesItems.html

* Added HTML tooltip support for Timeline

* Fixed tooltip position on Firefox

* Added Timeline tooltip example

* Updated tooltip location to be next to the mouse

* Added HTML element to example

* Fix redraw order

* Add initial itemVisibleFrame

* Add visibleFrameTemplate option

* Improve example

* Rename and fix example

* Fix comments from PR

* Fix example

* generate individual css files; fixes #1969
* simplified css bundleing
* add new generated dist-css files
* use chart specific css files in the examples