atum checkpoint with additional properties

[salamonpavel]

Background

Checkpoints can carry extra information that would be really useful for further processing and data mining.

Goal

With each checkpoints a Map[String, String] could be saved, name checkpoint's additional properties holding any data useful for the user.

Optional features

Checkpoint labels - perhaps they could be implemented as checkpoint properties with no value. To consider.
Automatic properties - some properties can be "switched on" on AtumAgent level and automatically added to each checkpoint created. Like Spark application id.
Querying checkpoints based on properties