Fixes #15:
1. Remove some very horrible code, a little work toward merging multiple groupings but it's too difficult for this ticket, fixes #157
2. Fix bug in grouping and disable useless double grouping but coalesce group projects is totally broken
3. Fix bugs in inlining projects into group

fix double grouping bug, enable complicated test case
Merge branch 'master' of github.com:slamdata/slamengine
shift array elements of rhs during array concat, fixes #167; add explanatory comment
Merge pull request #169 from jdegoes/ready/167

Fixes #167