* Replaces the hardcoded "config" keyword.
* Implemented by a compile-time option called `DATASTORE_TOP_SYMBOL` option in clixon_custom.h
* Tests: added endtest to all tests. Removed all premature exits if BE=0
* Except `CLICON_RESTCONF_DIR` which remains in clixon-config.yang due to bootstrapping
* -d <dir> option removed
* This applies to both evhtp and fcgi RESTCONF
* Both can also read config from backend, and be started from backend
* You may need to move config as follows (from clixon-config.yang to clixon-restconf.yang)
* CLICON_RESTCONF_PRETTY -> restconf/pretty
* CLICON_RESTCONF_PATH -> restconf/fcgi-path
* Not backward compatible: All uses of the ca-auth callback in restconf plugins must be changed
* New version is: `int ca_auth(h, req, auth_type, authp, userp)`
* where `auth_type` is the requested authentication-type (none, client-cert or user-defined)
* `authp` is the returned authentication flag
* `userp` is the returned associated authenticated user
* and the return value is three-valued: -1: Error, 0: ignored, 1: OK
* For more info see [clixon-docs](https://clixon-docs.readthedocs.io/en/latest/restconf.html)
* New clixon-restconf@2020-12-30.yang revision
