Tooltip / popover - support more positioning options

[pkozlowski-opensource]

In addition to the default top, bottom, left and right we should add support for top-left, top-right, bottom-left and bottom-right.

The positioning service is already capable of calculating proper coordinates, the only remaining part is to take care of proper arrows positioning. In angular-ui/bootstrap we were doing this directly in the positioning service but IMO we should try to do it directly in the popover / tooltip window directives (add more CSS rules).

[pkozlowski-opensource]

Bonus: if we do this we could use popovers to display date / time pickers in popups.

[pkozlowski-opensource]

twbs/bootstrap@8ef66df might change things for us in respect to this issue.

[intellix]

Tried using these as there's nothing stopping me and saw that bottom-left works but not bottom-right is a bit wappy: http://plnkr.co/edit/PoZ8fBskiCkcKeZ1Chvt?p=preview

Actually, tried all of them and the wrong ones are:

• top-right
• right-bottom
• bottom-right
• left-top

I'm on it though and a PR will follow