Make C++ online bagger

[cbrxyz]

The online bagger tool is a super helpful tool made by Kevin that allows us to store bagged information about important events, after they happen. This makes diagnosing events much easier, since we can easily get the data that led to the event happening!

The bagger should support:

• A config file for customizing its parameters (its history length, topic names, bag locations)
• Service to write the history for a group of topics to disk (ie, calling /bagger/record with {topic_group: "odom", history: 30} would write the last 30 seconds of odom-related topic data to disk)
• Re-subscribes to a topic if it goes down/is not visible
• Action server/client for showing progress of writing file to disk