Feature/issue autocomplete

Adds autocomplete for textareas - you get a github-like autocomplete for issue numbers, if you start typing "#...".

This works for work package numbers, as well as single words from the work packages subject:

![selection_103](https://f.cloud.github.com/assets/206108/1713063/5accd20a-6183-11e3-8163-d479172388be.png)

![selection_104](https://f.cloud.github.com/assets/206108/1713066/5e7a9c2a-6183-11e3-9c13-83b904571df1.png)

You can choose autocomplete options with arrow keys and &lt;enter&gt;. If an item is selected, the items work package id is inserted.