Refactor|Log: Added bits for target audience, more LOG_* macros

It is now possible to mark log entries for specific user groups
and/or domains. While the DEV group is intended for pure programmer
stuff (like pointer values etc.), the other groups are for domain
specific information (things like map elements, input events, or
OpenGL details).

The DEBUG and TRACE levels were removed and replaced with
DEV|VERBOSE and DEV|XVERBOSE, respectively.

Todo: Take the new macros into use in the libs and engine subsystems.
Todo: Filter history / alert selectively based on the new bits.