Support filtering datasets by both value and category URIs

[arteymix]

We need to add support for specifying both value and category because certain term fall within multiple categories (see https://github.com/PavlidisLab/GemmaCuration/issues/355). This is needed by GemBrow for correctness.

I see two options at this time for implementing this:

• allowing one AND to be nested within sub-clause
• adding a special property (i.e. allCharacteristics.valueUriAndCategoryUri) that handle a special value (i.e. {categoryUri}|{valueUri}) to create a special subquery using an AND clause

[arteymix]

We're currently using a workaround in GemBrow by requiring a dataset to have a factor with a certain category and a factor with a certain value.

This works as long as there are no factor with overlapping terms or categories attached to a given dataset. For example:

"disease" and "Alzheimer's"

Would incorrectly match a dataset with the following terms:

• "disease" and "Parkinson"
• "disease model" and "Alzheimer's"

The workaround was proposed by @oganm.

[arteymix]

A more general approach would be to add support for conjunctions within subclauses. It would play well with subqueries. This would be a pretty significant change to the filtering logic though.

[arteymix]

This is basically the same issue we face in #885. This could be a quite involving feature because it will affect how our subqueries are generated.