PROV-835 Starting point of authentication reimplementation

Moved core authentication out of ca_users and removed old/unused legacy
code that at some point was supposed to allow implementation of custom
Auth backends.

Still work in progress. Don’t use this yet!
PROV-835 Move password verification to LegacyAuthAdapter
PROV-835 Added PBKDF2 password hashing functions

Uses hash_pbkdf2 which is available in php 5.5+ and otherwise falls
back to custom implementation that requires the hash extension, which,
as far as I can tell, is part of most PHP setups (tested Debian, CentOS
and homebrew on Mac).
PROV-835 Implemented support for creating users via AuthenticationManager

Implementations for Legacy (md5-based) and CaUsers (pbkdf2 hashing) are
already working.
PROV-835 Throw exception correctly
Merge branch 'develop' into authentication
NOJIRA No more stray meow files in /tmp :-)
PROV-835 Basic infrastructure for "forgot password" feature
PROV-835 Work on password reset email workflow

Still unfinished, do not use yet!
PROV-835 Might as well use the full length of SHA256 for pbkdf2
PROV-835 First kind of working version of password reset

Still a ton of exception handling to do
PROV-835 Various password reset improvements
PROV-835 Almost working version of authentication rewrite including password reset
PROV-835 Send message when account is deactivated

Also deactivate account in the isValidToken() phase of the protocol,
not only in requestPasswordReset()
PROV-835 Writing and formatting

Got rid of all the text placeholders and applied some reasonable
formatting/styling. This probably still needs work but it’s not
completely embarrassing anymore.
PROV-835 Now allow authentication backends link to their own account management on the login page
PROV-835 Change interface in preparation for LDAP
Merge branch 'develop' into authentication
PROV-835 Rewrite OpenLDAP support in new infrastructure
PROV-835 OpenLDAP working reasonably well