Speed up ConfigRawParams and ConfigRawParamsTree reload time

[EosBandi]

A new Planner setting checkbox called "Running on a slow computer" controls how the ConfigRawParams and ConfigRawParamsTree pages are reloaded. If enabled, it keeps the metadata info and refreshes only the values and the control. For safety, there is a button to refresh the whole table (without reloading parameters from the vehicle).

Time improvements: Measured on an Intel Baytrail T Z3735F Quad Core stick computer with 2GB RAM
original Running on Slow Computer
ConfigRawParams reload 13sec 2.4 sec
ConfigRawParamsTree reload 20sec 3.5 sec

Note: Initial opening times of these pages are not improved; that needs a significant rewrite of the ParameterMetadataRpository, which is not in the scope yet.

[AppVeyorBot]

✅ Build MissionPlanner 1.0.3168 completed (commit 0bf9054757 by @EosBandi)

[meee1]

this doesn't violate any cross thread gui calls does it? ie the paralell.for's etc would

[EosBandi]

Paralell fors was there, I simply made the rowlist static. None of the two controls are used elsewhere and it just tests OK. So it did not break anything during testing.