Create utils for library refactoring

[lvrfrc87]

As part of refactoring, this is the first of a long PR series to make the code more readable.

All the utilities functions are now migrated under utils folder. Test are also added for each single utils.
Var and functions are also renamed and comment lines are also added.

More refactoring is needed as for example possible implementation for utilities under a single class, as well as improve the overall library logic. Those will follow after this PR as I first need to make the code more readable and have all the tests in place

[chadell]

not strong opinion, but I would simplify to netcompare/utils/ instead of an extra nested package for each group of functions.
Same for tests, I usually prefer to put all tests together, even in subfolders:
tests/check_type.py & tests/utils/check_refkey.py ...

[chadell]

good one. just some naming "suggestions"

[lvrfrc87]

@grelleum I am doing some refactoring in the code. I have managed to make all the test work apart the nested list implementation. Is something I can look at tomorrow but I was wondering if you can spare 10 minutes on it as you can quickly spot the issue and speedup the work.

@chadell considering there is some work to do in matters of comments and doc string, would you mind to have a fresh look at this PR??

[lvrfrc87]

@grelleum Nevermind, I fixed :)

[pszulczewski]

Needs improvements mainly in type hints.

[lvrfrc87]

I will go ahead and merge this PR so we can use an updated version of master for the coming PRs