Update CLI documentation

[Miles-Garnsey]

##Summary

The current CLI documentation at the home page needs some love.

Currently, using options such as --region='us-west-2' will yield an exception:

Exception in thread "main" com.beust.jcommander.ParameterException: There should be exactly 3 main parameters but 5 were found

The CLI help text itself remains correct, as it is generated via the jcommander configurations.

Proposed changes

The offending text comes from a file manual/src/includes/help.txt which seems to not be regenerated at build. I suggest adding a Gradle build task which pipes the relevant help output into this file when the project is built.

Within the help build files, this will induce a dependancy on a full build of the project.