More PHPdocs tweaks

[StrikeForceZero]

• Some IDE's may complain on process() line#260 that the return of getMessages is a string when it is in fact a string array.
• might as well add the @throws ClientException for getMessages while we are in here as well.
• constructor doesn't exactly return a void, so we can remove that (PhpStorm likes to highlight everything...)
• Closure is a root namespace class

:)

[marcelog]

Thanks!