[AESH-162]
added a simple graphics api. look at AeshGraphicsExample for an example
[AESH-147]
added cursor position to CommandLineCompletionParser.findCompleteObject
completion status might be wrong when user tries to complete a value that do not
have any value. argument completion will then kick in, but it might not be correct.
[AESH-163]
pressing tab should not rewrite the line when no completions are found
CommandValidator.validate(..) argument should be configurable
[AESH-164]
added overrideRequires, it will override missing Options that otherwise
are required by the Command