New Flood IF on OSM Building

Hi @Charlotte-Morgan @timlinux @cchristelis @mbernasocchi, this PR:
- addresses https://github.com/AIFDR/inasafe/issues/1237. So, if the hazard is raster, it will categorise the impact layer into 3 categories: inundated (equal or above threshold), wet (below threshold but not dry), and dry. For the vector, it will do the same like the old one. The impact layer will look like: 
![new_if](https://cloud.githubusercontent.com/assets/992519/4626406/ba3cd1d2-5380-11e4-9eeb-61f67f66d913.png)
- Please give some feedbacks on the impact layer style and the name for each category.
- This PR needs translation updates
- I assume there are a lot of failing tests (will look at it if you are all happy with this result)
- After you're happy with this changes, I will duplicate this for Tsunami On Building IF and configure some things to address #1238 (Update: Default value - tsunami impact on people)  and #502 (Name of Tsunami Impact Function is not valid)