Adding source(s) to datapoint entry page

[sarahf]

• A text field for adding a source, followed by a drop down menu signifying whether it is one of the following: newspaper, tv, radio, blog, NGO, government, social media, informant, other
• Option to add multiple sources, (with plus sign)

[jeromegv]

For the plus sign, I used one of the standard bootstrap icon http://twitter.github.com/bootstrap/base-css.html#icons There's quite a lot of icons included with bootstrap and they could potentially be used somewhere else, quite easy to implement. if you think it would look nice somewhere else, feel free to add it directly