capture exceptions thrown by the MongoDB driver
remove debug print
default debug level to 1 (the old behavior)
capture log and detailedLog from backend; print one or the other depending on debugLevel
use scalaz.Either.fromTryCatchNonFatal
feedback on REPL when setting debug level; extend Error
go back to Task.fail for evaluator errors

revert change to use \/ inside the Task
instead, fix the handling of failure in the backend to wrap the
exception with LoggedError
ADT for DebugLevel
clean up diff
make handling of unrecognized DebugLevel code explicit
always escape literals

literals almost always need to be wrapped in $literal for use with
Project, and there seems to be no harm in wrapping them even if in some
other case it might not be necessary
Merge pull request #112 from mossprescott/issue110-clean

always escape literals
rename showDebugLevel function
#110: log physical plan in BSON form
delete commented code
delete commented code
Merge branch 'trap-evaluation-errors' of github.com:mossprescott/slamengine-1 into trap-evaluation-errors
delete file again
Merge pull request #109 from mossprescott/trap-evaluation-errors

capture exceptions thrown by the MongoDB driver
Merge pull request #113 from mossprescott/issue111

#111: log physical plan in BSON form