alphasort the whole keydict before outputing files

This makes it easier to compare previous versions of the files since the
order should stay the same.  This also makes writing tests easier.
write test of 'sameness', keysync should gen same file that it reads

for example, `keysync -i pidgin -o pidgin` should generate the exact same
files, given that the input file is alphasorted.  This test currently fails
for a number of reasons, so it does not report as broken yet (|| true).
pidgin: update logic for including XMPP Resource to get correct output

Pidgin sometimes requires that the XMPP Resource is included in the
account name in OTR files.  This updates the code to do this correctly in
the cases that I am aware of.
use keydict key as canonical account name, key['name'] stores the app's name

For example, Adium uses account numbers, so given a keydict key of
gptest@jabber.org, a key read from Adium will have something like
key['name'] == 1
add tests for sameness between adium and pidgin, refs #1888

This shows that we have work to do:

* a lookup table for app-specific protocol names, refs #1964
* support multiple keys per id/name, refs #1871, #1868
* figure out zero padding problems, refs #1867
keysync-gui: detect if pymtp is available, and use it if its there

Before, pymtp was only used on Mac OS X, which has no MTP support. But it
turns out to be useful on GNU/Linux as well.  Sometimes gvfs FUSE mounting
fails to be available, but then the MTP send_file_from_file still works.

refs #1939
support pymtp v0.0.6, which has essential bug fixes

refs #1939
set version to 0.2.0beta1 in prep for upcoming release
keysync-gui: handle MTP connection errors better, and show a popup error

refs #1967, #1968
python-potr has been released, so special instructions are no longer needed