WIP refactoring IR builder
Refactored IR, all tests now run except fmrdd (currently disabled)
More progress on the refactoring.

For example, private vars of base classes are now supported again.
Fix various issues related to building the IR

- Enables previously disabled test (run/transient2.scala)
- Fix an erroneous test that expected duplicate fields
  (run/singleton-hierarchy.scala)
- Improve compilation speed
WIP, a new go at reworking the IR
Fixing merge conflicts, review @phaller
Adding transient2 test using (approx) Spark clases
Fixes for the IR builder refactoring

- Re-adds sharing support to new runtime pickler
- Smaller fixes here and there
Cleaning up the IR refactoring
Merge pull request #163 from scala/wip-refactor-ir

Refactoring IR builder