Share: add options for controlling workspace

[martin-henz]

In addition to the current option of choosing the language and variants via the query string, we should support the following:

• run: run the program automatically
• control the tabs: run program in CSE machine, or stepper, or display the data visualizer
• control the resources: make the number of steps or the runtime limits controllable
• full screen: we should support running programs in full-screen mode