Re-introduce lost functionality

The branch merged in 5a863589b4 removed fine-grained configure-time control
over install paths. This is necessary to accomodate various linux distros'
policies, eg. Gentoo wants games installed in /usr/games, but with resource
files in /usr/share/games.

DOCDIR and MANDIR appear to be unused, and were not re-introduced.
cleanup

-   drop trailing slashes from paths for consistency
-   sort entries that got unsorted
Improve actor movement collision handling
Use a better method to do actor physics traces
Get rid of the old newtrace method
Clean up the trace struct
Fix tracing down
Integrate unshield with launcher
unshield fixes
fix invalid syntax
filenames
anonymous namespace
enum was unnecessary
Install uncompressed data files from cd
cmake for system libunshield
 only use unshield on not windows