Fix #45 Update rho utils

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Includes all changes mentioned in issue #45

I changed/added a few options/tools:

1. added a progressbar (from progressbar2 python package)

also now most of the func have a two-level output printing (1st is the progressbar)

2. load_reps() function can load local, global representation and returns typed arrays
3. also have some function to build reaction representations from atomic reps

but maybe we don't need that one anymore?

Let me know if something looks wrong or useless

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I'll also try to add tests for the main functionalities!

[YAY-C]

• Changed the progressbar module everywhere.
  And added one kwarg for it (and left the printlevel as it was)
• Added a scrdir parameter to the load_reps()
• Made tests for load_reps() and load_mols()

[briling]

Could you please resolve the older comments (those which are not about is None)?

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Let me know if you feel like the comments are not clear enough!

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I think I found an ok solution

• created a function to evaluate the data

Let me know if it reads better!
also I made a few tests, but some more could be useful maybe