Make the behavior with workspace tabs the same as Dynamo's one

- disable removing `Home workspace`;
- disable having more than one `Home workspace`;
- disable editing workspace name in NWK (leave it allowed in web browser);
- set custom node workspace name from a dialog, `Home workspace` name should be "Home".

PR about setting a workspace tab name from its file is submitted [here](https://github.com/pboyer/flood/pull/65)