Generic cleanup Metrics and Losses

[JimClarke5]

This PR effects both losses and metrics.

This PR cleans up generic parameters to cut down on the number of unique parameters to at most 1 where possible.
For example:
public abstract class Metric<U extends TNumber, T extends TNumber> {
becomes
public abstract class Metric<T extends TNumber> {

and

@Override
  public <V extends TNumber> List<Op> updateStateList(Operand<U> values, Operand<V> sampleWeights) {

Changes to:

 public List<Op> updateStateList(
      Operand<? extends TNumber> values, Operand<? extends TNumber> sampleWeights) 

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[JimClarke5]

@karllessard @Craigacp @rnett Could one of you clue me in what went wrong here. I rebased the project to the latest master, but it still seem to pick up a lot of the commits from the metrics1 branch, that were applied with yesterday's merge.

[rnett]

Only time I've seen that happen is when I didn't update my local master, or I had a commit in my branch (that wasn't in master) from before master's latest commit.

Can you cherry pick the commits you want to a new branch? That's how I've handled it.

[JimClarke5]

I found this article which sort of explains how to do it. Seems overly complicated.
How to Fix Your Git Branches After a Rebase

[Craigacp]

I second Ryan's suggestion of git cherry-pick. Make a new branch from master, run cherry pick giving it the commits that should be in this PR, then force push that branch over this one (or make a new pr from the new branch).

There are other ways to fix it, but it depends on what the exact state of your git repo is.

[JimClarke5]

I had master->metrics1->generic_cleanup

I pulled yesterday's merge to my master from the main TF repository.
Then did a rebase of generic_cleanup to my master.

Based on recreating generic_cleanup with cherry-pick,
should I fix this PR? I assume cancel/replace.

[Craigacp]

A force push will fix it, but it'll require a bit of a renaming dance with the branches (i.e. cherry-pick to new branch, delete old branch, rename new branch to old branch, force push). It's up to you whichever you find easiest.

[JimClarke5]

Rebuilt the branch to exclude commits already included in master.