fix(dir[px-grid]): add `uiGrid.isRowSelectable` and drop `uiGrid.enableSelectAll`
fix(dir[px-grid]): add `uiGrid.isRowSelectable` and drop `uiGrid.enableSelectAll`

- Use `uiGrid.isRowSelectable` callback
    - https://github.com/angular-ui/ui-grid/issues/3743#issuecomment-164827461
	- Fixes #48

- Drop `uiGrid.enableSelectAll`
    - Apparently it caused headers issues
	- Anyway... it stil defaults to `true`

panaxit/panaxui-angularjs,panaxit/panaxui-angularjs