Wind Trail : add final windrun vector as a string at bottom showing distance and angle about weewx-polarwindplot HOT 1 OPEN

Implemented a net windrun label on trail plots. Trail plots now have a label similar to the following on each plot:

Net windrun 2345km from 223°(SW)

The label defaults to the bottom left of the plot but will (should) move around to automatically deconflict with the location of the timestamp label. New config option vector_location implemented to control the location. Usage is as per time_stamp_location eg

vector_location = bottom, left

or

vector_location = top, centre

or

vector_location = bottom, center

etc

refer commit c313b69

Need to do some more testing to make sure that net windrun label and timestamp automatically deconflict their locations. (ie they never appear in the same spot!)

from weewx-polarwindplot.