#301: Generalize pubkey checksum display and check

pubkey:checksum format is displayed and can be passed to all commands. The checksum is validated.

Splits check_public_key() function into three functions:

• is_pubkey_and_check()
• check_pubkey_formet()
• validate_checksum()
• gen_checksum()

Create display_pubkey_with_checksum() function

Creates and update related tests.

Close #301 (closed), #320 (closed).