Extend DescribeSuite to have a test cases run against all three ethereum txn types

[timbrinded]

rather than having to manually bake in the logic for deriving the test case ids, create a new test case function callback provided by describeSuite() which auto calculates this for you.

example:

it({id:"T01", title:"normal test" ..... })

itEth({title:"normal test" ..... })

in addition to testcase auto calc, it should provide a txnType string literal available to that context, so that any test logic can make use of that var in its tests.

N.B. Investigate if we can remove test case IDs entirely!