Fixes\Additions for 0.9.0-RC3

- Added implicits for converting JTS geometries to geotrellis features.
- Added SeqSource, HistrogramSource type aliases
- Overloads of RasterSource.mapIntersecting for convenience.
- Mimic Op[T]'s io.Collect, by creating a SeqSource[T] out of a sequence of DataSource[_, T]
- Fixed a bug with reading Bit rasters with a different RasterExtent.