install_requires corresponding to pip requirements

So that `python setup.py install` yields a functional Mailpile.
Ignore expired or revoked secret keys during setup
Fixed a missing NoSuchMailboxError import statement
Fixed another missing import statement.
python-jinja2 listed as dependency for Debian
spambayes package suggested to Debian users
Update translation template
New .po files from newly updated translation template (locale/mailpile.pot)
Icelandic translation
Some fixes, corrections and new translations
Compiled .mo files
Adding missing mailbox import, issue #399
Merge pull request #418 from neilbartley/ignore_expired_revoked_sec_keys

Ignore expired or revoked secret keys during setup
Merge pull request #405 from gthb/patch-2

install_requires corresponding to pip requirements
Merge pull request #436 from boltronics/deb_fix

Required dependencies missing from debian/control
Added rough rudimentary responsive support for topbar
Added rough implementation of message 'Textual User Generated' Signatures to a JS modal add/update tool
Refactored sidebar CSS a bit to use table-cell and vertical alignment to resolve Issue #419
Refactored show Cc, Bcc and added ability to hide fields as per Issue #415
Fixed Keybinding support as per Issue #438
Tweaked responsive things that show & hide a bit, especially in thread (also fixed wrong padding around avatar)