Remove IntrinsicSymbol

- Encode fields in raw tables as Select(tableNode, field) instead of
  Select(Ref(IntrinsicSymbol(tableNode)), field).

- Simplify WrappedQuery. Encoding a new path starting at the wrapped
  Node's IntrinsicSymbol was unnecessary.

- In DistributedDriver, use RefId (resurrected from Slick 1.0) to create
  unique identifiers for TableNodes.

- Remove the "inline" phase. It is no longer necessary.

- Remove orphan node logic from Dump. Trees really are trees now, not
  just forests.
Merge pull request #740 from slick/tmp/remove-intrinsicsymbol

Remove IntrinsicSymbol