QuantumPhaseEstimation takes BigEndian argument

[crazy4pi314]

Describe the bug
I think this is just an inconsistency, most everything uses LittleEndian and the controlRegister argument takes a BigEndian.

Expected behavior
I would expect the signature for QuantumPhaseEstimation to be

    operation QuantumPhaseEstimation (
        oracle : DiscreteOracle, 
        targetState : Qubit[], 
        controlRegister : LittleEndian
    ) 
    : Unit is Adj + Ctl{
...
}

[guenp]

After some thought it looks like this won't be a straightforward fix so we are going to include this in #337, so will close this for now. Thanks @crazy4pi314 for raising this issue!

[guenp]

Reopening this issue and assigning our new Status-ChildIssue label so we can track it as part of the #337 proposal.