explicitly set using gradient image

This may latter be exposed as a parameter

Change-Id: I694de874aaaf22c9428c4fe02b2cfebce3181ddb
Adding convergence parameters to gradient descent optimizer

Change-Id: If7f07ea7c25baef749cf0b7a3af2ef743a66c5af
WIP: Add LBFGSBOptimzerv4 and AmoebaOptimizerv4