Implement function to filter cve entries by entry type

[CermakM]

• example usage: cve_sub_list = extract_entries_by_type(cve_items=cve_list, entry_type='app')

• specify TODOs and suggestions in cve.py

• additional minor changes

modified: cve.py

Signed-off-by: Marek Cermak macermak@redhat.com

[tisnik]

One minor issue: the code won't pass pydocstyle check with following settings used across f8a repositories:

[pycodestyle]
ignore = E121, E126, E402
max-line-length = 100

(I know, that this script is not part of any official repo yet, but you might want to get used to run linters :)