Add additional permissions for changing signal attributes

[bartjkdp]

We would like to add some more permissions so we can configure access more gradually:

• Changing signal type
• Changing signal urgence
• Changing signal location

Some suggestions from @CBuiVNG:

• Changing signal reporter
• Changing signal directing department
• Changing routing

Currently a user is able to do these things with one general permission sia_write.

Also we could shortly discuss the impact of both requiring sia_write and sia_signal_change_* for specific actions, as this makes the system less flexible.

Migration

We can make this change non-breaking by adding a migration that adds the specific change permissions for all users that currently have sia_write.