move default ASPROOT to XDG_CACHE_HOME or similar
move default ASPROOT to XDG_CACHE_HOME or similar

Others have asked for this in the past, see:

https://github.com/falconindy/asp/issues/7#issuecomment-57004965
https://github.com/falconindy/asp/pull/9

asp might get more traction with the prospect of it more widely
replacing ABS, and I suspect this will come up again.

falconindy/asp