index bookmark checkbox, purely bootstrap grids

I was still having trouble with the 'bookmark' checkbox alignment, esp on small screens. 

![bookmarks-search-results-weird-collapse](https://f.cloud.github.com/assets/149304/1921957/789e9d60-7e00-11e3-832d-6044c982056d.png)

To fix and make it easier to deal with, I tried to stick closer to bootstrap -- removed all the floats involved, and now just plain using the standard bootstrap grid feature. 

Adjusted number of bootstrap columns to leave enough room for bookmarks checkbox and label (including longer 'In Bookmarks' label) at each size. 

Provided lower margin on collapse, to leave enough spacing between bookmark control and following. 

The class `documentFunctions` was being used on the 'show tools' as well as this bookmarks checkbox, pretty different elements in terms of layout, making it hard to style appropriately. For the index page 'bookmarks' use, changed to class `index-document-functions`. 

medium sized viewport:

![bookmark-fixed-not-collapsed](https://f.cloud.github.com/assets/149304/1921994/f3fb67d6-7e00-11e3-9657-085ba947fdfd.png)

collapsed small viewport:

![bookmark-fixed-collapsed](https://f.cloud.github.com/assets/149304/1921999/f9516190-7e00-11e3-812c-f1985b50e0ce.png)