Replace 'hover' deprecated pseudo-event

'hover' pseudo-event has been deprecated in jQuery 1.9.0,
use of 'mouseenter' and 'mouseleave' instead.
Merge pull request #519 from loris/patch-1

Replace 'hover' deprecated pseudo-event
Merge pull request #517 from ckosmowski/master

Add the distance delay to the header drag code.
Fix #520 - dropstart event not firing
Use of navigator.userAgent instead of $.browser

$.browser object has been removed from jQuery 1.9.0
Merge pull request #521 from loris/patch-1

Use of navigator.userAgent instead of $.browser
Merge pull request #523 from ckosmowski/master

Distance for dragging
Shift+arrow keys support for selection
Use a URL instead of a path for the wiki link in the README

GitHub currently transforms the path into a blob-style URL for the wiki, which is a 404
Merge pull request #535 from tombenner/master

Fix wiki link in README
Changes according Pull request #534

numeric keycodes
{} for ifs
Merge pull request #534 from fetis/master

Shift+arrow keys support for selection
Add multi-level grouping to DataView.
Based on the original pull request (https://github.com/mleibman/SlickGrid/pull/522) by ghiscoding.

Deprecated DataVIew APIs (will continue to work):
- .groupBy()
- .setAggregators()

New DataView APIs:
- .getGrouping()
- .setGrouping(groupingInfo)
- .setGrouping([groupingInfo1, groupingInfo2, ...])
- .collapseAllGroups()
- .collapseAllGroups(level)
- .expandAllGroups()
- .expandAllGroups(level)
- .collapseGroup(groupingKey)
- .collapseGroup(level1value, level2value, ...)
- .expandGroup(groupingKey)
- .expandGroup(level1value, level2value, ...)

Grouping info options (for use in .setGrouping() calls):
- getter
- formatter
- comparer
- aggregators
- aggregateCollapsed
- aggregateChildGroups
- collapsed

New Group fields:
- level
- groups
- groupingKey

Also fixed 0-handling in default aggregators.
Optimize up DataView aggregation.
Column option for 'focusable' needs a default value. Set to true, as that's the default behavior assumed by 'canCellBeActive'
No longer need to check if columns[cell].focusable is a boolean: since every column now is boolean by default, we simply return focusable at the end of the function. (The original 'return true;' is not needed because the default value here IS true.)
Merge pull request #538 from dariusk/master

Adding default focusable column option, plus minor optimization to canCellBeActive
Adding default value for selectable in column options, optimizing canCellBeSelected.
Merge pull request #540 from dariusk/master

Default selectable column option, minor optimization of canCellBeSelected
Added support for predefined group values to DataView.

New grouping info properties:
- predefinedValues - An array containing the grouping values for which
groups should be included even if they are empty.
- aggregateEmpty - Whether aggreggators should be run on empty groups.