This represents a portion of the refactoring that I had intended to do
until I realized that there was a simpler solution to the problem that
we were having (having proguic add stored calculated values to the
defaults object).
So ideally we'll continue extracting all quote init code out of
`Server' and into `ProgramInit' in the future.
* doc/server.texi (Liza Server): Mention `ProgramInit'.
* src/program/ProgramInit.js: Add class.
* src/server/DocumentServer.js: Use it.
* src/server/Server.js (_progInit): Add private field.
(__construct): Accept ProgramInit instance and assign to field.
(initQuote): Use promise returned by `_getDefaultBucket'.
(_getDefaultBucket): Proxy to `ProgramInit#init', which returns a
promise.
Mike Gerwitz