Add some helper functions in Plan
Remove some redundant tests from HeftPlannerTest
Use lists of VMTypes internally in HeftPlanner

Instead of Map<VMType, Integer>
In Planners take an initialPlan instead of VMTypes

* A plan can store a list of initially available VMs in the same way as
  Map<VMType, Integer> vmNumbers.

* But it also allows the planner to allocate more VMs if it is allowed.

* Additionally this allows us to mess with the schedule before the
  planner can begin e.g. to have certain Resources (aka VMs) only active
  for some of the simulation.

* Finally it will allow the use of these algorithms for ensembles of
  workflows.
Add a Builder for StaticHeterogeneousAlgorithm
In HeftPlannerTest test the interface not the implementation
Add VMType.getProvisioningDelayEstimation()

Since there is already a getDeprovisioningDelayEstimation() it makes
sense to have this.
Add optional start and terminate times to Resource

This will allow us to have create static plans where VMs are started and
stopped as needed.

Note that these are not yet handled by the two Static Algorithm classes,
so don't do anything yet.