oggm_shop fixes

[Morlocke]

I've updated and fixed oggm_shop within my abilities:

• I've tested nearly every combination of parameters I can think of and it doesn't crash or not work on any of them any more (see the exceptions below where fixes are needed on the OGGM side) - a couple of minor fixes were necessary
• get_tidewater_termini now works again
• remove_RGI_folder now works again
• server paths have been added as parameters to the conf file and replaced accordingly in the code
• read_glathida majorly cleaned up

Remaining known issues:

• 'consensus_ice_thickness' returns 0 thickness everywhere with RGI 7.0C and G - doesn't crash or give an error, so this must be an OGGM server problem (all good with RGI 6.0)
• 'its_live' returns no velocity observations for RGI 7.0G (fine for C though), so this is also on the OGGM side (all good with RGI 6.0)
• I have not tested the 'preprocess' parameter and its two associated dependecies, 'dx' and 'border', because I agree with Fabien's comment in the code that this is a use case that should almost never come up. Also, you need to be more familiar with OGGM to make it work, so I'm going to leave it alone
• All other parameters and parameter combinations that I could come up with work fine. I don't think we can ever pass a list of RGI_IDs to OGGM, though, because I don't think it supports it. We have to do one call per RGI ID, so this can be done for a list either with a bash script or having hydra scan over a list.
• I'm not entirely sure I understand how the tests work (how do you flag a test as fast, slow, etc., for instance? People probably need to be told you need to install pytest separately as it's not in the default IGM environment. How do you even run the tests (I can work that one out)?). And there seems to be no documentation on them, which is ironic. But, in terms of testing oggm_shop, all you need to do is load the default conf file and check you get an input.nc file with some values in out the other end. Happy to write it if someone can give me some pointers on how to do so.