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;
- set custom node workspace name from a dialog, `Home workspace` name should be "Home".

It would be better to merge first:
- https://github.com/pboyer/flood/pull/64 (without this changes opening won't work at all);
- https://github.com/pboyer/flood/pull/65 (with this changes tab name will be updated by file name).
Sorry @marimano , we need to keep this behavior.  There are two ways of thinking about flood.

1) Dynamo web app - Relies on MongoDB to persist workspace names.  In this app, like flood, it should be easy to change workspace names.
2)  Dynamo node-webkit - This relies on Dynamo for workspace names.  In this mode we need to persist the names with the file.

In node-webkit, we need to disable setting the name except for via Save As.  We don't need to disable setting the workspace name entirely.