lib: create lib `f-tools`

[ximenesyuri]

Description

One should have a library which provides the needed tools to develop with f-utils. It should be a CLI that provides the command f with the following options:

1. f i/info some_spec other_spec ... -f/--from /path/to/some/file.py -f/--from ...: search for the provided specs in the given paths and prints f.spec.info(spec) for them for the obtained spec
2. f j/json path/to/ref.json --from /path/to/file.py --from ... -c/--conf path/to/f.py: generate a ref.json file with all info from the provided files according to configurations in a f.py file
3. f r/ref path/to/ref.md --from /path/to/ref.json -c/--conf path/to/f.py: generate a reference manual from the provided json file according to configurations in a f.py file.
4. f t/test some_spec other_spec ... -f/--from path/to/file.f.py -f/--from path/to/other/file.f.py: search for the provided specs in the given paths and execute "spectrum unity tests" (think about that) for that.