Properly do roll-up stats when vecs change

Cache roll-up info; produce it on demand; display it in the Inspect2
page.
Clean up enum-producing code, in prep to doing more cleanup.
Merge branch 'master' of github.com:0xdata/h2o
Much more extensive JSON support

Nested structures will print out nested JSON.
Arrays of Iced will JSON.
Nested structures will auto-doc-gen all nested classes.
Fix bug with chunks that got written-to, not cleaning up state.
Frame reports byteSize for whole frame.
Include Vec._mean in the rollups.
Add README.txt info for top-level zip package.
Add README.txt stub for R package.
Merge branch 'master' of github.com:0xdata/h2o
Add LICENSE.txt to zip package.
py test.py --help shows the new -bf switch:
  -bf, --beta_features  enable or switch to beta features (import2/parse2)

py test_from_import.py -bf
will, for example, use ImportFiles2.json and Parse2.json
(putfile not there so only tests that import will start to work)..
H2O Parse2 might not be a complete json response yet (redirect stuff?0
Merge branch 'master' of github.com:0xdata/h2o
well, at least this makes the names in h2o_cmd.py more consistent
typo if verobse (storeview_import).