New plugins and collectors and lots of optimizations.

- list_terminals plugin
- weak query dependencies
- component reflection
- nicer printing of entity-related classes
- fixed issues with reverse lookups and identity indexing
- there is now only one identity class (that's down from, like, 8)
- new expressions: LetEach and LetAny
- preliminary support for tracking cost and usage of lookup tables
- query analyzer now suggests indexing as well as deps
- all find functions now support complete results
- support for parsing arbitrary entities
- parsing terminal ring buffers

BUG=
R=scudette@gmail.com

Review URL: https://codereview.appspot.com/159310043