user-configurable expandableRowHeaderColDef

[jadelane]

Related to issue #1990.

This allows the user to configure the expandableRowHeaderColDef by adding a $scope.gridOptions.expandableRowHeaderColDef to js files.

[PaulL1]

I'm OK with this in concept, but two requests:

1. Could we add ngdoc for the option? The format is pretty straightforward, for example starting at line 27 in the file. We'd also typically do the defaulting/initialisation in the initializeGrid method, rather than inline at the point you're using it (take a look at the top of the file to see what I mean)
2. Could we put an example of this into the tutorial, or at least mention it in the tutorial? The tutorial files are in misc/tutorial/*.ngdoc

@jpuri, I'd also be interested in any comment you may have on this.

[jpuri]

Please use var declaration for variables you are declaring. I could not find one for userInjectedExpandableRowHeaderColDef and finalExpandableRowHeaderColDef. Also code styling in the if block needs to be corrected.

[jpuri]

Hey @PaulL1 PR looks fine to me. It will give users ability to customize row headers for expandable rows. I have added suggestions about the code changes @jadelane please check those.

[jadelane]

@PaulL1, Pull Request is ready for review again

[c0bra]

@jadelane if you're able, it would be really good to rebase these commits into one single commit.

I would do it on my end but you'd be lost as the author and I wouldn't want you lose your "contributorship" :)

[JLLeitschuh]

@c0bra You could allow them to keep authorship: http://stackoverflow.com/a/3308780/3708426

[JayHuang]

This PR seems to cause the Expand All button/icon to disappear and show "Expandable Buttons" in its place.

[mportuga]

@jadelane I am closing this PR for now since it has conflicts and @JayHuang pointed to a possible issue with it. Feel free to open a new one if you still wish to contribute.