minor code touces.

* tests: Also check samples_db for wltc-class mismattches.
tests: Treat all wltp_db vehicles as Class3b.

* core: Possible to override WLTC-class.
* tests: Add Downscale-comparison test for wltp_db vehicles.
wltp_db: Test-metrics for transplanting-gears in the core.

* core: possible to override calculated_gears (transplanting) before
driveability-rules.
* core: split cycle_run from driveability-rules.
* core: use DataFrame for storing tabular cycle-results.
* model: minor improve input of DFs for forced cycle, etc. 
* tests: wltp_db: extract method for researching on stored-cyles.
* tests: wltp_db: generate and compare also transplatted results.
* tests: use core transplanting of original-gears.
* deps: Upgrade jsonschems 1.4-->2.4 with fixed exceptions (github
#164).