mill-build: don't copy any assets, just make full paths
only 'inspect' when colours are on, otherwise 'log'
mill-build: config parser: also read input.output
bin/mill: closing status info respects --no-colors
combineFiles: combine in series (maybe async does wrong order)
build: fallback to empty values when making full paths
build: more assets
Merge pull request #14 from papermill/next

bugfixes