Add a unified and optionally more constrained API for expressing filters on columns

This is a re-opened version of:
https://github.com/Parquet/parquet-mr/pull/412

The idea behind this pull request is to add a way to express filters on columns using DSL that allows parquet visibility into what is being filtered and how. This visibility will allow us to make optimizations at read time, the biggest one being filtering entire row groups or pages of records without even reading them based on the statistics / metadata that is stored along with each row group or page.

Included in this api are interfaces for user defined predicates, which must operate at the value level by may opt in to operating at the row group / page level as well. This should make this new API a superset of the `parquet.filter` package. This new api will need to be reconciled with the column filters currently in the `parquet.filter` package, but I wanted to get feedback on this first.

A limitation in both this api and the old one is that you can't do cross-column filters, eg: columX > columnY.
no, no reason really. These structs are meant to be case classes essentially. They have final fields which point to other immutable classes.

If you think this is silly I can just move the toString bits to the toString method.