defining API for LDAP, the postgresql database as well as for the SFA
managers.
+CortexlabShell
+--------------
+
+**fill missing code in this class**
+
+This class contains methods to check reserved nodes, leases and launch/delete
+experiments on the testbed. Methods interacting with the testbed have
+to be completed.
Cortexlabnodes
---------------
+**fill missing code in this class**
+
CortexlabQueryTestbed class's goal is to get information from the testbed
about the site and its nodes.
There are two types of information about the nodes: