Fix previousOwner bug

Game did lose data of prev owner.
comments
Fix use of abs() for floating point arguments
fix typo and add exception
audible feedback for unload
Map Scripting.

hoo boy, this is a big one... i should probably split it up, but who cares?
at some point i'll need to write a big ass help doc/faq to go with this
to explain each command and how each variable interacts with it.
but in the meantime, i hope i've included enough examples and error messages
for common failure scenarios for the more adventurous of you to figure out
how it all goes together, and yes, this is fully capable of perfectly
replicating all of the TFTD map types, i've already got their scripts
assembled in the ruleset on my end.
i have plans to expand on this a little in the future,
like allowing certain commands to store their x/y values for use by others,
and allowing for multiple UFOs on a map, but this should do for now.

special thanks to Volutar for his help in getting this together.
fix out of bounds tile check
add static Cydonia based on PSX version of XCom

cause why the hell not?
redaction: size is only required commands referencing groups.
add resize map script command.
defaults: don't resize anything unless specified.
fix mem leak
fix up tftd tank draw routines
fix small glitch with built-in melee weapons
add damageType for terrain kersplosions.
fix typos in error checking code in MapBlock

fixes gcc-4.8.3 warning:
src/Ruleset/MapBlock.cpp:52:14: warning: & has lower precedence than !=; != will be evaluated first [-Wparentheses]
 if (_size_x & 10 != 0 || _size_y % 10 != 0)
             ^~~~~~~~~
src/Ruleset/MapBlock.cpp:52:14: note: place parentheses around the '!=' expression to silence this warning
 if (_size_x & 10 != 0 || _size_y % 10 != 0)
             ^
               (      )
src/Ruleset/MapBlock.cpp:52:14: note: place parentheses around the & expression to evaluate it first
 if (_size_x & 10 != 0 || _size_y % 10 != 0)
             ^
     (           )
Merge pull request #966 from myk002/fix_mapblock_warnings

fix typo in error checking code in MapBlock
Merge pull request #964 from louisdx/absfix

Fix use of abs() for floating point arguments
minor adjustments to mapscript

fix horrible resizing error, streamline destructor
Merge pull request #958 from Yankes/PreviousOwnerBug

Fix previousOwner bug