Dvc: completion: support import-url and get-url

[dnabanita7]

Add support for dvc import-url and dvc get-url into bash auto-completion script.

What should be done:

As to import-url and get-url, you would need to convert on ${COMP_WORDS[1]} first that would replace all - with _, so that option_list becomes _dvc_import_url and not _dvc_import-url.

[efiop]

Context https://github.com/iterative/dvc/pull/2226#issuecomment-511155421

[algomaster99]

@shcheklein Shall I take up this issue?

[efiop]

@algomaster99 Sure!