Avoid undefined columns in sortInfo

When using server side sorting, the init() method attempts to set
sortInfo.columns before $scope.columns is defined (before the
buildColumns method has executed). It throws an error, and the grid is
not displayed on the page.
Merge pull request #160 from andrewalker/master

Undefined columns in sortInfo
Fix for #151 and #148
hopefully fixing Aggregates once and for all!
It is done.
forgot a piece of code.
selections can now persist through aggregate changes.
adding selectAll and groupBy methods to options
adding sortBy method
updating flexible-height plugin
column pinning prototype.
simplified pinning logic
making z-index 5 and standard on selection cells.
binding z-index to pinned state in template
getting pinning working with aggregates.
linking aggCol pinning with Selection checkbox pinning

also not running a digest when adding an agg column.
adding pushpin icons
updating build to 1.9.0
Merge pull request #166 from angular-ui/pinning

adding column pinning v 1.9
setting pinning to be false by default