updated compile tests for new minimal AnalysisCallback
moved discovery to discovery/ subproject and updated for new approach
fixed discovery to only find public methods when searching for annotated definitions
extracting inherited definitions unimplemented in api/, so some discovery tests fail
moved discovery classes from sbt.inc package to sbt.compile
multi-project incremental compilation
and dependency management
'update' currently runs on every compile
built-in 'compile' command shadows 'compile' action