Change the API error handling system

[Desrever Nu]

We are still using a system that was initially designed with another idea in mind

[Sam Griffiths]

Errors are now handled by ErrorManager.java in the utils directory. Errors have been unified across wrappers and an attempt has been made to standardise the occasions when they are returned.
I feel that this may need some tweaking as different error cases appear but the new method should make this easier.