* Move pkhex.drawing calls out of form constructors
designer doesn't like it; if Main can't be designed then there's some
call that it can't process for whatever reason
* Add netcore3 targeting
Closes#2198 by adding a netcore3 build option
Closes#2391 by retaining designer functionality and net46 builds
remove silly idle loop, call close manually
remove initialization check for generating sprite; now only calls at max
2x when starting up = not necessary to bypass with a special variable
