m2crypto dependancy

[bennomadic]

after the xmppwebid revamp, currently we're only using it for pkcs12 certs.
do we want them on the release? they're a good fallback for some clients, but not
a high prio methinks (and currently p12 views are half-broken)

one option could be refactoring all the openssl calls to use m2crypto.
but for now we can stop using the p12 functionality and remove that dep