doc: Include list of TCs in doc

doc: Include list of TCs in doc

List of vsperf "inbox" testcases was added into documentation.
This patch also fixes:
* a few SPHINX warnings and errors
* empty userguide index

JIRA: VSPERF-519

Change-Id: I417ed40130f0c7de4f76551f3f1cac0cb1e6da89
Signed-off-by: Martin Klozik <martinx.klozik@intel.com>
Reviewed-by: Al Morton <acmorton@att.com>
Reviewed-by: Christian Trautman <ctrautma@redhat.com>
Reviewed-by: Sridhar Rao <sridhar.rao@spirent.com>
Reviewed-by: Trevor Cooper <trevor.cooper@intel.com>