[strongSwan-dev] WI: moving credential manager, sets

[Martin Willi]

Work-Item: moving credential manager, sets

Branch: master

Schedule: 4.4.1

Rationale:
PKCS#11 support (for 4.4.2) will support certificate storage on
smartcards. We abstract certificate stores in credential_sets registered
to the credential manager, but this framework is integrated in
libcharon. Our smartcard support should be available to other tools,
such as the 'pki' utility, or maybe at a later stage, pluto. We
therefore move the credential_manager and the credential_set interface
from libcharon to libstrongswan

API changes:
credential_manager.[ch], credential_set.h and sets/*.[ch] will be moved
from libcharon/credentials/ to libstrongswan/credentials. The instance
of credential_manager_t will move from the charon->credentials to the
lib->credmgr global variable. Update any plugins using trunstchain
mechanisms or registering own sets to the new locations.