gkeys: Update config file

Rename MAIN section to DEFAULT for automatic variable substitution to work
in sub-sections.
Add a new seeds subsection and rename the seed files for better user interaction.
Remove self.configparser.add_section('DEFAULT') from read_config()
gkeys: Update seed action options

Remove category option as it is not needed.
Add file option to installkey as it is needed in the listseed() call.
gkeys/actions.py: Make 'rel' category the default in listkey()
gkeys/cli.py: Update option help messages to better reflect how they may be used
gkeys: New checks.py and KeyChecks class

Move GkeysGPG.check_keys() code to the KeyChecks.validity_checks()
gkeys/checks.py: Use passed in logger instance
gkeys/actions.py: Update checkkey() to use the SeedHandler.load_category()
gkeys/check.py: Remove invalid long_keyid == keyid[2:] check for SUB key types

This caused it to not detect correctly and perform subkey checks because they subkey id is never
the same as the primary keyid being checked.
gkeys/check.py: Add sign check for PUB type keys
gkeys/actions.py: Output the key being checked

Add a logger.info and an output line indicating the key being checked.
gkeys: Fix spacing issues in the print output

For failed items, replace the ( ) around the nick with < > for consistency with
normal coding, also add a space between hte name and nick.
Add an indent space for the failed headers.
Modify print_output() to indent the data.
Merge pull request #32 from gentoo/dol-sen-PR

Improvements in key checking