Add full support for permissions on OS-level primitives

[DonOregano]

Currently (as of 6.1 RC1) we set all OS-level primitives to be world read-write, which will allow any user to connect to a Dob run by any other user.
This was primarily a fix to solve #271 and #272.

This behaviour should really be configurable.

We need to add requirements about what should be possible to do in this area, we need to add tests and we should make all of this configurable.

[DonOregano]

This should also make sure that whatever we decide to do with permissions we also have a proper solution for #271.

[DonOregano]

Also consider how to play nicely with umask on Linux.

[DonOregano]

Current implementation does not set all os primitives to world read-write as indicated above. At least two issues have been found:

• File locks in StartupSynchronizer need to have their permissions set. This solution appears to work: https://stackoverflow.com/questions/910528/how-to-change-the-acls-from-c
• NamedSemaphore needs to add Global\ as a prefix to the semaphore names for other users to be able to access the semaphores.

More issues can probably be found, this needs thorough testing.

[DonOregano]

Some of these issues have proof-of-concept fixes for windows in be8c2c7. Needs thorough cleanup and Linux implementation.