Clean up and centralise edit status for Timeline Items.

* Fix redraw order
* Fix error when option is not defined
* Allow template labels
* Add .travis.yml file
* Add experiment travis code
* Fix react example
* Fix bug in item editable

* 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 groupEditable
* Fix group drag in vertical direction bug
* Fix indentation
* Add initial nestedGroups property
* Fix redraw order
* Get nested groups hiding working
* Add order to nestedGroups
* Fix up example
* Add support for intially closed nested groups
* Add nested groups indentation
* Fix indents
* Add nested groups docs
* Fix example
* Revert indents
* Add classes to nested and nesting group labels and add nesting group css
* Use pure css for nested group icons
* Remove commented off lines and unnecessary btn
* Fix indents
* Add support to showNested:false in group
* Add semicolon
* Remove empty lines

* Fix redraw order

* Add initial itemVisibleFrame

* Add visibleFrameTemplate option

* Improve example

* Rename and fix example

* Fix comments from PR

* Fix example

* Fixed bug introduced in #2284 where overrideItems is set to true when boolean is provided
* Added the option of supplying object to item.editable with updateTime, updateGroup, and remove functioning similarly to timeline.editable but only on a single item
* Updated Documentation to reflect the new feature
* Updated the individualEditableItems example page to show feature usage.

* Timeline:
* Add overrideItems sub-property to timeline.editable
* Change behavior to override item.editable when overrideItems=true
* Added new example for timeline/editing to higlight differeing editable behaviors.
* Update timeline doc to reflect addition of timeline.editable.overrideItems
* Timeline - fixed logic oversights found in editable override testing
* Timeline - enable changeGroup when item.editable = true and not overriden
* Timeline - Small format changes to documentation and example pages for overrideItems

* Add initial onChange item tooltip
* Add example and tooltipOnItemEdit template option
* Add docs and rename option
* Fix docs
* Fix example
* Change example's item types
* Fix point item tooltip
* Fix comments from PR and support bottom orientation properly
* Add semi-colon

@simo9000 Thanks!

* Hide vertically hidden ranged items in groups that are not visible
* Add element to templates options
* Fix comment typo
* Add documentation for react mounting
* add react example
* Fix typo
* fix title
* Fix review comments
* Add vis-drag-center to fix dragging bug when template is react component

* Hide vertically hidden ranged items in groups that are not visible
* Add element to templates options
* Fix comment typo
* Add documentation for react mounting
* add react example
* Fix typo
* fix title
* Fix review comments

* Hide vertically hidden ranged items in groups that are not visible
* Fix misspelling
* Fix examples that do not contain groups
* Add example for vertical hidden ranged items
* Fix indent format in RangeItem
* Fix example
* Fix other examples after addition of vertical hiding range items in groups
* Add case of zero margin axis
* Fix commented out lines in examples
* Fix vertical visibility bug

* Hide vertically hidden ranged items in groups that are not visible
* Add element to templates options
* Fix comment typo
* Add documentation for react mounting

Timeline will check for the property 'editable' on individual items.

  if editable === true
    ignore timeline option 'editable'
    allow item to be edited
  else if editable === false
    ignore timeline option 'editable'
    do not allow item to be edited
  else
    use timeline option 'editable'

If two items are selected and one is not editable, only the editable
item is draggable.

This change required the css class .vis-editable be moved from the
item set to the individual item containers to maintain proper styling.

If the dataAttributes config option = 'all' then write every field as
data-? attributes on the element.

Read from an array of allowed dataAttributes at the timeline level and
write them as data- attributes on the item