* Fixed a bug in the ProtonMail importers (pmkey-*.py) where multiple
keys found for a username would always result in the last email
address checked being returned in the printed output for all located
keys.
* Mostly tightening up the details on the hkp4py example script.
* Also fixed a typo in the LGPL boiler plate text included in all the
other example scripts for the HOWTO.
* lang/python/docs/GPGMEpythonHOWTOen.org: Updated links to the
ProtonMail keyserver import scripts and added a warning regarding
being unable to update third party keys.
* lang/python/examples/howto/pmkey-import-alt.py: added usage.
* lang/python/examples/howto/pmkey-import.py: added usage.
* import-key.py: fixed a minor typo.
* pmkey-import.py: locates and imports keys from the ProtonMail keyserver.
* pmkey-import-alt.py: the same as the previous except with setting an
alternative $GNUPGHOME directory.
