Make DEFAULTs public
Rename query.h to api.h
Rename query.h to api.h and update references
Rename query.cpp to api.cpp also
Add Query base class
Show how the new API done for Add Task
Rename ADD_TASK to AddTask, clashing but conforming
Move files to its correct filters
Gregorian -> Posix time
Merge pull request #68 from evansb/simplify-api

Simplify QueryEngine API