Support purs executable

[nwolverson]

This is changes to support 0.11, not to build under 0.11. Was probably just going to put up a follow-up commit on this branch that does the latter.

• Support new imports list format with module name
• Retaining support for psc-ide-server and old imports list format

[nwolverson]

@kRITZCREEK I notice that compiler PROTOCOL.md shows import list result as

"moduleName": "MyModule"

but I see

"moduleName": [ "MyModule" ]