Some modifications to program structure and implementation of queue.

1)Vessel.java
- Added startTime variable;
- Implemented Comparable interface (to allow processing in PriorityQueue).

2)RadarSimulator.java
- Changed data structure from array to HashMap for storing vessels;
- Added queue for storing vessels over maximum amount;
- Added PriorityQueue for vessels with a later start time;
- Modified update, add and remove methods consequently;
- Exported most of data processing to VMS.java.

3)VMS.java
- Added some elements from RadarSimulator.java, such as data[][] array;
- Modified update function;
- Simplified risk calculating algorithm.

4)Driver.java
- Made a few adjustments to reflect changes in above classes.

Other changes (FilterPanel.java, TablePanel.java, MapPanel.java):
- Added label to filter;
- Changed display of map to make ships bigger, and display circles for alerts;
- Fixed issue where new ships were not appearing in the table.

- Cleaned up code, added some comments.
Merge branch 'master' of https://github.com/pmlt/comp354

Merging to validate commit.