Correct Bootstrap tooltip positioning for top and bottom options

####Bootstrap tooltips don’t behave nicely

This is a response to issue #5130
Moving away from mootools introduce a nice glitch of bootstrap tooltips: their position for the options top and bottom is far from optimal:
On horizontal placement of a label:
![screen shot 2014-11-18 at 10 38 35](https://cloud.githubusercontent.com/assets/3889375/5095729/fbec85b8-6f74-11e4-934b-c17330822250.png)

And on vertical:
![screen shot 2014-11-18 at 10 49 52](https://cloud.githubusercontent.com/assets/3889375/5095770/463ab824-6f75-11e4-890c-832cdfa5ef94.png)

Here are the proposed placement with this PR:
Horizontal:
![screen shot 2014-11-18 at 10 39 30](https://cloud.githubusercontent.com/assets/3889375/5095791/7cd179f4-6f75-11e4-9647-2750b468c887.png)

Vertical:
![screen shot 2014-11-18 at 10 53 02](https://cloud.githubusercontent.com/assets/3889375/5095828/b7935594-6f75-11e4-90c9-1987ceebe893.png)

Tooltips render nicely even on small screens.

#####There is a change in text alignment on form-horizontal from right to left (the first two pictures illustrate this)

This is the default in a LTR document, it shouldn't need to be specified.