Introduce reconfig suites, for dot1q+ip4+vxlan

Ticket: CSIT-1551

+ Config copied from other suites.
+ Layer keywords prepared for additional chains.
+ Renamed "create" argument to "vlan_per_chain".
+ TrafficGenerator result extraction improvements.
 + Also unified TG type and subtype checking.
+ Throughput estimated as PDR for zero PLR.
+ Actual Qemu start is skipped.
+ Parse xstats instead of stats in trex stop scipt.
 - Because stats are unconditionally cleared on each script connect.
+ Remember start values to get better ReceiveMeasurementResult at stop.
+ Expose loss count and time as appropriate test message.
+ Autogen support.
+ Multiple chain amounts and core densities.
 - Only 1 additional chain.
+ Proper TAGs. Documented.
 + Clarified min framesize tags are for TG-DUT.
  + Added a TODO concerning overhead values.
 + Added 118B tag.
+ Robot performance keywords improvements.
 + Added missing return value documentation.
 + Frame size as required test variable, not an explicit argument.
 + MLRsearch keyword to store result (not into test message).
  - TODO: De-duplicate: main keyword to measure, minor to set test message.
   - But implementation uses the fact default arguments are different.
 + Keywords for starting and stopping background traffic.
  - No checks whether start-stop pair is complete.
+ Multiple minor indentation and logging improvements.
- Missing / TODOs:
 - Support also vlan_per_chain=True?
 - Support dot1q without vxlan?
 - Support also deletion?
 - How to package config steps so -reconf can be generated from -ndrpdr?

Change-Id: If0270697f9ffa837c34ef802917220a53f156703
Signed-off-by: Vratko Polak <vrpolak@cisco.com>
(cherry picked from commit ff820e3d53434889aacde2373314c3be8d00f765)