improve commands, proper build/project base resolution
improve commands, proper build/project base resolution

finish alias support
better project printing in 'projects'
completion support for 'help'
resolve URIs in ProjectRef against base URI of defining build in keys and project relations
resolve base directories and record build URI in BuildUnit
preserve relative paths in File to URI conversion for later resolution

sbt/sbt,xuwei-k/xsbt,mdedetrich/sbt,mdedetrich/sbt,mdedetrich/sbt,sbt/sbt,xuwei-k/xsbt,sbt/sbt,xuwei-k/xsbt,sbt/sbt,Duhemm/util,mdedetrich/sbt,xuwei-k/xsbt,xuwei-k/xsbt,sbt/sbt,sbt/sbt,sbt/sbt,mdedetrich/sbt,mdedetrich/sbt,mdedetrich/sbt