Implement robust way to do rough alignment

[arentkievits]

To come to a more robust results, it's probably better to split the point match candidate finding and RANSAC. To do this, use routines in features.py.

Originally posted by @arentkievits in #2 (comment)

[arentkievits]

https://github.com/AllenInstitute/render-python-apps/tree/master/renderapps/section_polygons Idea for filtering matches based on section outlines

[arentkievits]

Also allow for importing to TrakEM2 for manual landmark alignment and importing of resulting stack back to render-ws