take advantage of tsserver model of code for faster TypeScript builds

[zpdDG4gta8XKpMCd]

• VSCode Version: 1.2
• OS Version: Windows 7, x64

Currently a way to build a TypeScript project is to run a console command (tsc) that works separately from the tsserver. It looks like the the build could have been done faster if the model of code stored in the tsserver was used that is already parsed, bound and partially typechecked.

[dbaeumer]

Closing as dup of the exploration item in the June iteration plan here: #7253

[dbaeumer]

Still keeping it open since the iteration plan doesn't explicitly talk about emitting. But the idea is to use the tsserver for emit and project level type checking.

[dbaeumer]

@waderyan this ask for the builder and compileOnSave work we are discussing with the TS team.