SES-1798 : Spell-check javadoc and api methods with american dictionary
SES-1798 : Add ParserConfig addNonFatalError and getNonFatalError

Also override useDefaults from RioConfig so that it wipes
non-fatal-errors at the same time as it wiped the settings for those
errors.
SES-1798 : Expand javadoc for DatatypeHandler and LanguageHandler
SES-1798 : Fix another instance of language in DatatypeHandler javadoc