#108 FR237 - Battle Window Opens in position it was last closed

[triplelafayette]

Patch file attached (and also attached to the feature request ticket as well)

Feature request - https://sourceforge.net/p/triplea/feature-requests/237

Change Summary:
Essentially for the battle window to open in the last position it was closed (multiple monitor case given and desire for window to keep opening up on a second monitor).

Implemented essentially by adding a couple of static variables to track position and size. If they are null we get default behavior, when the window closes they are set. When the window is opened we use any value that is set. It is not thread safe, but - doesn't matter so much.

[redrum]

Committed. Excellent work!