certs: more filters, better initial uid selection, code cosmetics

    - add three types of filters for certificate list (ui looks like crap
      there, need to work on that)
    - select uncertified uids by default in CertifyKeyActivity
    - move some code around in KeychainProvider, 's slightly less hacky now
certify: preserve user id certificates when saving secret keys
Merge branch 'certify' into certs

Conflicts:
	OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpKeyOperation.java
	OpenPGP-Keychain/src/main/res/values/strings.xml