Implement streams and tasks import/export features

[jvalkeal]

It could work like this

• Adding scdfsi and scdfti languages allow us to do syntax highlighting and to special processing via language server.
• For streams and tasks we would work via Export Streams and Export Tasks which simply opens json given us by server
• From import language itself we can add import command which allows user to pick environment where to import.;
• And usual vscode chores around all these.

[jvalkeal]

It would be theoretically possible to do things like Import to Env... which asks target env and then does things automatically. This might be too much magic happening and was kinda reason why it wasn't done for app imports from known urls. As we anyway need to have a support to go via this intermediate step, then automating further is easy step in a future.

[jvalkeal]

Thins needs an api support from dataflow.