bugfix: use statements in multi-line comments of included spec do not
cause errors markers any more

-every use statement has to be defined in its own line (like the
engine requires it, too)
-decode method in AbstractError now throws an exception if an unknown
error kind occurs

Change-Id: Ia03511e3838b68f37ed253ac510196c7da120677
Signed-off-by: mdausend <github@dausend.net>