Bootstrap dropdown

Douglas - Here's some working dropdowns for bootstrap. I didn't have to do too much "hacking" to get it to work.

Few comments:
 - I added the dropdown to bootstrap.css, and removed all the 'reset' styles. Also added the downloaded bootstrap.js (NB: I put this under static/webtagging/3rd-party/ to keep it separate from your code. You might want to do the same with bootstrap.css.

 - I had to add <div style="position:relative"> around the drop-down button as a container for the dropdown list. You might be able to add style="position:relative" to the <th> or other container.

 - You'll need to bind the tag dialog etc to the <a> tags in the dropdown list, using the .on() method we discussed earlier.

 - I also removed your .showTag styles from webtagging.css since I don't think you need them when the pane is shown within the webclient?