Support Expression JSON

[araddon]

Expression needs to support to/from json to allow json api usage.

• re-implement the custom AST objects (filterstatement, etc) as Node interfaces
  • new Include
  • new BooleanNode
  • parser/ast uses new objects
• node logic Elide, simplification to easiest form, collapsing single boolean/binaries.
• vm supports new boolean, include
• new simpler anonymous embed Expr for Json
• cleanup old code in Node, Parse tree, VM that is no longer used or makes sense or not idiomatic
• part of #99 allow custom validation for functions, allow a interface for func, validation
• Allow different func registries per evaluation context (es) instead of falling back to global
• downstream conversion 100% on queries, expressions
• Value, NodeArray ensure are 100% tested and implemented in Protobuf, Json Conversions
• test the hell out of this
  • new tests for escaping table.field name type identities.
  • new round-trip test's with both protobuf, json
• new simpler anonymous embed Expr for Protobuf
• implement ToEs()