Missing file
- fixed .gitingore to not exclude TestResult.cs
- added TestResult.cs

Output results
- results now display average time (=total time/iterations) instead of just the total time for all iterations
- Delegated actual printing of test results to TestResult class
- Reflowed code to print as tests finish instead of waiting till completion (noticeable for long runs)

GCM wrapper changes
- Allowed null inputs (gives null outputs)
- changed IV to simple RNG instead of crypto RNG since GCM can work with simple IVs (unlike AES CBC that needs crypto RNG IVs)