LU code refactor

[boydc2014]

Recent change in Lu flow #660 did a couple of things

• Split a single state ”isPublished" to "lastUpdateTime and lastPublishTime" to be more flexible and reduce race condition
• Move luStatus out of luisSettings.json, because they are supposed to couple toghether
• Some simplication of not trying to support multiple luis remote apps, once user change app name, clean the generated folder

which are good things. But there are also many issues with it, which should be fixed before we move on

• our convention and interfaces of indexers are broken, luIndexer takes too much responsibility
• lots of reduplicated code in luIndexer
• uncenessary interfaces like IOperationLUFile, ILuisStatusOperation, which looks like bad design, and the callers of it must be not pretty
• poor namings like preLufileParsedContentLUISJsonStructure updateLuInMemoryIfCreate
• some poor interface design
• the timing of cleaning up the generated folder is confusing