Change default massivity of castle ground tiles.

This was driving me mad.
Reorganize authors.txt file.

It now gives a much better overview of all the copyright holders
plus conact information (the latter is stripped out for the credits
screen in the game). Specialthanks people who have helped the game,
but not contributed code or assets, hence do not hold copyright,
have been extracted into a separate file (which is also read for
the credits screen).
Revert commit 93a94a1ca54bb2f762719f262401ca6786fd4534 and add missing copyright notices.

That commit incorrectly assigned the entire copyright to “The
SMC Contributors” (later changed to TSC Contributors). As we have
officially forked the game, we can’t simply swallow FluXy’s
copyright notice. This commit re-adds it for legal clarification,
and adds the TSC copyright notice below it. Copyright notices of
other external copyright holders have not been touched.

This commit also adds copyright notice headers to all files that
were missing one.