#681 Update from JUnit 3 to 4

[David Benn]

See https://objectcomputing.com/resources/publications/sett/august-2007-migrating-from-junit-3-to-junit-4-nothing-but-good-news

This will modernise VStar's UTs and permit use of tools such as https://github.com/pholser/junit-quickcheck

[David Benn]

Experimented with JUnit 4 and created two JUnit 4 unit test classes that sit alongside existing ones for:
phase plot calcs
VeLa

In addition, for those new classes, property-based unit tests were also added using JUnit QuickCheck. This approach shows promise given that PBT generates n > 1 actual test cases for a given PBT test case function.

Moving to JUnit 4 will require additional dependent libraries over and above the JUnit jar and a careful consideration of the licences of these libraries will be necessary. It may be that we need to move to Maven or something else that brings in the required libraries since it may not be possible to have them under version control. Then again, perhaps it will be possible to make a distinction between libs that form part of what is re-distributed in VStar itself vs test libs.

Ultimately should move to JUnit 5.