borrow variable name splitting code from kep parser

[epogrebnyak]

This can be a helper function in db package:

https://github.com/mini-kep/parser-rosstat-kep/blob/master/src/csv2df/util_label.py

We also need a listing of variable units of measurement descriptions, similar to #39, this can be also borrowed from here:

https://github.com/mini-kep/parser-rosstat-kep/blob/c0a4941202484127193146045a095d1fc6b2e8cc/src/csv2df/specification.py#L74-L84

[epogrebnyak]

@ignaloidas - need to import test for the functions as well

[epogrebnyak]

@ignaloidas - I suggest sticking to the rule who opend the issue - closes it, or the maintainer. It helps to keep track of if the originator person is really satisfied with what was done.

[epogrebnyak]

@ignaloidas - there shoudl be a file tests/test_labels.py, the test for labels.py are mixed in test_utils.py