tidying MAN

[CB-quakemodel]

This PR cleans the MAN module in the following ways:

• All python modules have been cleaned (removing unused imports, ordering imports, adding the GEM copyright to top of each file, consistent formatting and for functions with many inputs making them one input per line to make less cluttered)

• Moving similar sets of functions into the same python modules. For example, the functions pertaining to mfds and rates have all been moved into a single module, rather than being dispersed as before.

• Cleaning up the tests - the data for each test is now separate and clearly labelled, as before they were in mixed directories).

• Cleaning the notebooks to be more readily usable and updating the imports to match the new MAN module structure.

• I remove the csv_site function as it is very arbitrary (just prints a site amp function), and also the unit tests are incomplete (they are just a string which I guess was going to be the expected results of using this function, but I see no test data or unit test classes here either).

• Better defining each set of functions. For example the functions which work on a single source typology are now stored in a folder called single_source_utils rather than just single which was a bit ambiguous. Another example is the checks directory, which is now called checking_utils and has more clearly defined python modules within it - the MFD and rates functions 2 separate modules both called mfd.py, and a module called rates.py and have been merged into a single python module given they were heavily interlinked (the new module is called mfds_and_rates.py)

[kejohnso]

I need to think about this change.... I don't think I'm exaggerating when I say it would break 100s of my scripts but I do understand the point changing the submodule organization