DIRAC v7r1

MySQL versions supported

[TECH PREVIEW] MySQL version 8 is now in pre-supported mode: the tests that we have done didn't show any issue, but are not conclusive.

Dynamic instantiation of the FileCatalog plugins

FileCatalog is now instantiating plugins using ObjectLoader mechanism, which allows to provide plugins in extensions. One side effect is that SecurityPolicy plugins are dropped and the only one exisiting VOMSPolicy became VOMSSecurityManager. For those installations that used PolicyBasedSecurityManager, the configuration should be changed in order to use VOMSSecurityManager instead.