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ARROW-4741: [Java] Add missing type javadoc and enable checkstyle

This change:
1.   Enables a check style rule on all public, protected and package visible classes/enums.
2.   Adds missing javadocs to make the rule pass
3.   Adds some private constructors to static method utility classes (some of these are  little bit short, and in some cases especially flight some of the purposes of classes was a littler hard to infer).
4.   Cleans up redundant public qualifier on interfaces when found.

Author: Micah Kornfield <emkornfield@gmail.com>

Closes #4374 from emkornfield/class_javadoc and squashes the following commits:

10ff97a <Micah Kornfield> fix last gandiva issue
cb3175b <Micah Kornfield> Fix gandiva docs
32a4a18 <Micah Kornfield> address review feedback
a64f658 <Micah Kornfield> the rest of the classes
3e3d6d6 <Micah Kornfield> ARROW-4741: Add type javadoc.