Integration docs: HelloWorld and other basic examples.

Integration docs: HelloWorld and other basic examples.

This patch adds to Integration docs some simple testcase examples
like a HelloWorld. The purpose is to show how to use some basic
features: rules on L3/L4 fields, MultiStream, Multi-VM setup.

Patch Set 2: removed trailing whitespaces.

Patch Set 3: moved the examples to the middle of the file to avoid
potential conflicts with the VxLan TC patch from Sugesh.

Patch Set 4: fix typo.

Patch Set 5: added descriptions on each example.

Patch Set 6: reworked description for VM Replacement TC.

JIRA: VSPERF-331

Change-Id: I9dea23c26138db874fd67f41d8de8a628db5d91f
Signed-off-by: Antonio Fischetti <antonio.fischetti@intel.com>
Reviewed-by: Maryam Tahhan <maryam.tahhan@intel.com>
Reviewed-by: Martin Klozik <martinx.klozik@intel.com>