see https://basarat.gitbooks.io/typescript/content/docs/tips/nominalTyping.html and https://github.com/Microsoft/TypeScript/blob/7b48a182c05ea4dea81bab73ecbbe9e013a79e99/src/compiler/types.ts#L693-L698

Fixes #8402

Fixes an exception was being caused because the panel was not initialized
when calling into createNew. This also fixes multiple terminal instances being
spawned if the panel WAS initialized but contained 0 processes.

Fixes #8209

This change also consistently hides the terminal when exiting the final
terminal.

Fixes #8211

Fixes #8139

Fixes #7034

Part of #7034

Fixes #7189

Fixes #6892

Fixes #6683
Fixes #6762

Part of #143