Add new configuration for setting key stores. The new 'key-store'
statement allows users to configure key store backends. These can be
of type 'file' (that works the same as 'key-directory') or of type
'pkcs11'. In the latter case, keys should be stored in a HSM that is
accessible through a PKCS#11 interface.
Keys configured within 'dnssec-policy' can now also use the 'key-store'
option to set a specific key store.
Update the checkconf test to accomodate for the new configuration.
a035f3b10e