Added class testing FloodDisaster, with one test
Added method for creating water based on Position
Added to Position: constructor using other Position
Moved methods from FloodDisaster to World
Added test for FloodDisaster

New tests verifies that no flood appears when the chance is 0.0.
Also moved setup code to setup() method.
Added and corrected javadoc in FloodDisasterTest
Merge branch 'test-flooddisaster'