python linsys solver improvements

[bamos]

• Add support for other precision.
• Decide if anything else should be passed back up to Python.
• Add normalization.
• Add some docs and a description somewhere.
• Add more checks to the functions passed in to make sure they are reasonable/take the correct number of arguments since otherwise errors coming from C calling back into Python can be uninformative/unnecessarily long
• Add in standard normalization routines to the library users can call if they don't want to implement their own