Aper adding wcs and support for various input data

I think this one needs more work, but can be merge as is if you prefer:

- [x] support more input data types
- [x] add unit test
- [x] add/change documentation
- [x] support more input coordinate formats
- [x] return user input coordinates and pixelcoordinates in the result table

Future:
~~accept non pixel unit for radius etc. when the wcs is provided.~~ Moved to future feature list in #131

Just a thought - do we want to add ``unit`` as a keyword argument, which a user can use to specify the units of the data in case they cannot pass a quantity for the data?