isolate: code drop from upstream moe.git

Imported d331139bdbc6b2a7a1a1f318970734888324730b
isolate: update moe code drop.

github.com/bblackham/moe-cms.git 8d83ff6bb1692b23c802b8fbb395f05244e8f819
Add infrastructure to compile isolate.
Convert to use isolate instead of mo-box.
Remove mo-box from source tree.
Initialize sandbox automatically on worker startup.
Don't error when timer or mem usage unknown.