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
no longer has any dependencies
small ProcessLogger interface to send buffered out/err to
commented out (but working) implicit conversions from Logger -> ProcessLogger
for use in an integrating project to get original functionality