Sort Subcommands in Command Reference

Not sure which order or structure is applied in the [Command Reference](https://github.com/crmsh/crmsh/blob/master/doc/crm.8.adoc#command-reference) section of the manpage.

IMHO, it is a bit hard to find the needed information. :) As such, I would like to suggest the following changes:
- Sort the subcommands in alphabetical order.

The manpage is a reference, so it's natural to list commands and its subcommands in alphabetical order. It's easier to find if you scrolls down.
- Group common subsubcommands like `cd`, `up`, etc. into its own section.

You could name it "Common (Sub-)Commands" or the like.
- Add a short description for the main subcommands.

For example, the section about `cib` could be named: `cib -- CIB Shadow Management`. For consistency reasons, it would makes sense to use the same text as you've used in `crm help`.
Descriptions in subcommands are probably not needed as the names are usually clear enough. However, it helps the reader (and his eyes) a lot to see this (optical) distinction between a subcommand (only one word) and its main command (one word plus a short description).