[Trellis-developers] changes to error constants

[Shaddy]

Before:

EM_ERRORMESG = 'error message'
EC_ERRORCODE = error code


Now:

TRELLIS_E_ERRORCODE = error code
$TRELLIS_errors[TRELLIS_E_ERRORCODE] = 'error message'


Benefits:

messages can be customized on a per client or per mod basis
error constant is prefixed with TRELLIS_ to ensure uniqueness


Notes:

Both methods will be available for use at first, all new errors will be 
added in the new method only, support for the old method will be removed 
once the core has been updated.