ROIGeometry contains methods are not thread safe

[aaime]

They are currently using a field to store a point and a rectangle JTS geometries used for containment tests.
This is done to avoid generating a lot of garbage in case the contains methods are called repeatedly (which some operation does), however this makes the class stateful and prone to multithreading problems (with multiple threads all modifying the same point and polygon objects).

This commit fixes the erroenous behavior, but at a high performance price:
aaime@20330e5

Some other approach should probably be used... like a pool of these objects (but we'd need a very lightweight one), thread locals (but how to clean them up?) or... dunno, something else.

[aaime]

For example: https://github.com/DanielYWoo/fast-object-pool or even better https://github.com/chrisvest/stormpot