Removing Ship Explosions

Removed ship explosions due to spam in fastest speed setting.
Fixed Shipwrecks

Shipwrecks only occur when disasters are enabled, similar to plane
crashes.
Merge pull request #2 from ignatio/master

Changed Shipsprite to only cause wrecks when disasters are enabled
drawing-order: draw tiles right-to-left

to handle tall tiles correctly
gui: draw tool cursor using fillRect rather than drawLine

this should help with higher-resolution displays where the stroke
behavior can be unpredictable. It works better to use filled
shapes which are more predictable.
file-format: rewrite save() to use a new XML-based file format

a file format that I just made up
file-format: writeMap() use tags to indicate where new rows start
file-format: ability to read in history arrays from xml
file-format: complete XML load implementation
file-format: fix a bug in XML_Helper
file-format: use Boolean.toString rather than hardcoding "true"/"false"
file-format: move taxRate and budget levels from <misc> to <budget>
file-format: check gameLevel against range when reading from xml
file-format: markup history with <shortTerm> and <longTerm>
file-format: save/restore the "noDisasters" option
file-format: keep misc sanity checks in place
file-format: move timing information into <cityTime> child element
file-format: do not synthesize compatibility bits

since there's no software we need to be compatible with
file-format: use tile names instead of numbers (write only)
file-format: use tile names instead of numbers (load)

in addition, use :pwr suffix for any tile where the PWR bit is set