Don't use hashed files on dev

Doesn't use `asset.map`, and therefore hashed files on dev - meaning, no need to restart app when compiling assets. 

When running grunt, either pass `--dev` param, or set env variable `GRUNT_ISDEV=1`

Makes frontend development on fronts actually bareable  

 * no need for separate `compiled`, `generated` and `hashed` static target dirs
 * not dependent on running `hash` or `imagemin` tasks to compile assets
 * moved non-compiled assets into `public` dir

![anigif_enhanced-buzz-17391-1382438434-5](https://f.cloud.github.com/assets/74132/1406733/0ad39cbe-3d59-11e3-92b6-ee2ee2ddd83f.gif)