ISPN-2977 + ISPN-2978 Various CLI fixes

ISPN-2977 Report parser errors properly (instead of ignoring them and causing NullPointerExceptions)
ISPN-2978 Allow execution of statements using a throwaway session

https://issues.jboss.org/browse/ISPN-2977
https://issues.jboss.org/browse/ISPN-2978