Allow VSCode users to choose 'local' - e.g. per workspace userdir

[JaroslavTulach]

Some users of VSNetBeans complained that Language server in VSCode is mixing contents from different workspaces.

Sometimes I work with two checkouts of our repos, e.g. one on a brach that I'm currently actively working on,
and a second one to produce quick fixes, or to babysit a merge.

If I open both workspaces at the same time, then the language server seems to mix up the symbols from
the two workspaces.

... searching for a class finds two copies. The second one (located in src/...) is the correct one from this workspace.
The first one (located in ~/git/.../...) is from another workspace. In the second workspace it's the other way round
(i.e. the first one is correct and shows a project name, the second one shows a full path and is from the other workspace).

Closing the other workspace does not fix the issue, but restarting vscode does.

This PR offers the user to choose between global and local workspace. By using local one gets new instance of the NetBeans Language server backend per each workspace.