Clean up TOC entries for config sections

[dedemorton]

The Configuring... topics in all Beats docs have topics nested under them that begin with "Set up".

We should either be consistent and use "Configure" across the board, or reword the topic titles to match user goals. I'd prefer to reword the topic titles around user goals:

For example, under Configuring Packetbeat:

Set traffic capturing options > Capture traffic
Set up flows to monitor network traffic > Monitor network flows
Specify which processes to monitor > Monitor processes

[dedemorton]

@roncohen Just an FYI that this is what I have planned for the docs.

[dedemorton]

I'm planning to do some major reorganization of this content, so closing this issue in favor of spending time on that effort.