Add option to dump pilot files in JSON format

With current format settings, 1000x easier to read than raw files
Downside is that the files are much larger; ~33k-200k
    (size could be reduced by using a less readable format
    and relying on external JSON viewers)
Controlled by cmdline param -json_pilot
    (autoenabled in debug mode)
JSON format files use .plj & .csg as the extensions **NOTE** Commit log has a typo, should be .plj and .csj **END NOTE**
Could be extended in future to use JSON as pilotfile format
    (i.e. read in JSON)