Matrix unit tests fail intermittently

[pdavidc]

The unit tests for class Matrix fail intermittently due to the use of random numbers in unit tests. The failures are are difficult to reproduce and repair since the test conditions cannot be reproduced exactly.

[pdavidc]

Configured Matrix unit tests with a pre-determined random seed. The affected unit tests need only pseudorandom values, while using a known seed enables easy reproduction of test failures. Closed by commit a366ffe.