Removed unused Serializable interface...

...bumped level cap to 10 for some systems for enemy ships,
reworked systems to allow multiple systems,
added loading of ships with missing 'max' attribute on <crewCount> tag
Fixed two Linux-specific bugs...

...fixed hotkeys bugging out on Linux (actually caused by a bug in SWT
-- changing accelerator text also changes the accelerator itself),
Fixed grid not always being resized correctly,
Changed "No Crew" to "<No Crew>" for consistency
Update changelog.txt and version string
Bumped SWT version to 4.3.2