HeaderCellTemplate from column builder used, filter permitted on headerCell

Modify defaultColumnBuilder to add a headerCellFilter property to columnDef,
allowing a translate to be applied to the header without needing to use a custom
header template.

Modify ui-grid-header-cell directive to use the header template from the
column builder, rather than ignoring it.

Minor modifications to templates because the result of a compiled template
seems a little different than an inline template, and therefore some classes
ended up in different places within the ng-repeat.  This could alternatively
be fixed in the css, but css is really not my thing.

Noted that on my mac in chrome the column menus are not correctly attaching
to the columns, but I believe this is a pre-existing problem not caused by
this change.

The diff on ui-grid-header-cell.js makes it look like far more change than it is.  I've pushed the old link content into a compile - post, and written a new pre.  I didn't make any changes in the old link, but every line had to be indented so they all show as changed.