Rename filter variables and methods in DataApiRequest

[mpardesh]

Addresses #497

[archolewa]

Note that this is a breaking change (anybody who uses either of the getters in a request mapper will experience compile errors when they upgrade).

We generally try to avoid breaking changes, especially in small updates. Instead, we should add new methods with the desired names, and deprecate the old methods. Then we can remove the deprecated methods in a later major version rev, where breaking changes are more or less expected.

Also we should add a CHANGELOG.

[archolewa]

Forgot to use the Request Changes feature, and I can't do a blank request changes.

[archolewa]

These deprecated methods should delegate to the non-deprecated version (i.e. getFilters() should return getApiFilters(). Furthermore, we should add a Javadoc, with a @deprecated annotation indicating which method to use instead.

[archolewa]

This should just delegate to getDruidFilter.

[archolewa]

@mpardesh Just reviewed this change. Had a few small comments. Once those are addressed, I'll be willing to give my approval.

[michael-mclawhorn]

There's a problem with the underlying issue.

There's a reason that API filters are considered plural while Druid filters are singular. Because API filters are treated as a list (or a list grouped into a map by dimension) while the Druid filters are a tree with a leaf node as the reference variable.

[archolewa]

@michael-mclawhorn As far as I can tell, the api filters method is still called getApiFilters, while the druid filter is called getDruidFilter. So things are still plural and singular appropriately.

[michael-mclawhorn]

@archolewa Yeah, I see that.
I actually think I'd rather make a breaking change than each the deprecation cost here, but I suppose that's not the friendliest choice. This is going to create rebase pain with #501, so I'd merge it quickly if you don't want to fix it.