Keyserver: have limited amount of data in txt record

That fixes an avahi crash:
avahi-daemon: running [sapx230.local]: dns.c:806: avahi_dns_packet_append_record: Assertion `size <= 0xFFFF' failed.
Sections: First attempt to write emails

This fails for now as there bugs somewhere else, i.e. fopen
being used.
We have to merge a better working version.
Merge commit '5abe5c443bb90e86b1bcf3c9e46a9fdca9ed70a1' into email

for the fopen fix

Conflicts:
	Sections.py
	    meh, the change made on the email branch looks bigger than it is
Sections: Using the proper filename of the signed key and a real UID

This makes it send emails.
Well, it opens the email client of the user. Testing with Evolution.
It will be interesting to see how it will react when non-email-address UIDs will
be handled.

So far, subject and body are missing.
Sections: Introducing a subject and a body
temporary commit, encryption doesn't seem to work
Keyserver: Made it quit when pressing Ctrl+C, also serve a key off disk

Now, when testing GNOME Keysigning, you don't need to have two instances running.
You can start the keyserver with an exported key.
Merge branch 'keyserver_quit' into tobi_tmp_email
Sections: Introduced a UIDExport function to export a single UID

This is very likely needed for stripping everything but one UID.
Sections: Mailing the signed UID and the UID only

It requires a bit of a dance with GnuPG in order to strip off all other
but the signed UID, but it seems to work well enough for now.
Sections: Made it send a separate email for each UID

funnily enough, gnupg does not like to re-sign a key it seems.
And I cannot make it sign one UID at the moment. But that should be
possible.
Setting always-trust in UIDExport

Interestingly, the GnuPG wrapper was confused about gpg's output, which
indicated that it would look into the trustdb. We don't actually care,
so we tell that gpg.
Save the received and authenticated key in self.received_key_data
Strip, Sign, Encrypt and Mail every UID on the key
Merge commit '6bcd93310e960de274a522f088b9045141e03163' into email

for integration in the develop branch

Conflicts:
	Sections.py
	    develop wrapped the sign call in a try/catch block.
	    we do it, too.
Merge branch 'email' into email_to_develop

Conflicts:
	Sections.py
	    Completely took the other branch's logic.
Merge branch 'develop' into email_to_develop

We want to incorporate the latest changes to prepare merging

Conflicts:
	Sections.py
	    A comment and getting the key in recieved_key (sic!)
	    were conflicting.
	    Interestingly enough, the order of arguments for
	    display_downloaded_key seems to have changed.
	    But it seems to work well enough.
Merging email feature which allows sending an email to each UID
Sections: Monkeypatched monkeysign's build_command
Sections: Added a MinimalExport function to get minimised output from keydata

This could and should somewhere more central.