handle leading groups in the concat functions in the pipeline phase
Merge github.com:slamdata/slamengine into feature/#15
ongoing work to group by support'
introduce schemachange
tests for schema change
oodles of supporting machinery
bug fixing
sketch out remaining cases in pipelinebuilder.unify
sketch out implementations for concat and some other functions
simplify
checkpoint before major refactoring
moving stuff from the expr op phase to the pipeline phase
sometimes you need an expression
add safety
refactor to make nest index like nest field
code tightening
port more functions over from expr phase to pipeline phase
delete legacy developer notes
add Project.getAll to mirror setAll
code cleanup