Minor tidy to some JSPs

The "Replace assessment package content" JSPs for the standalone and LTI
interfaces have been unified. (Still cut & paste though, yuck!) And a
few fixes to capitalisation elsewhere.
Updated Maven plugins to latest versions
Updated library deps to latest versions
Ported use of Charsets.* from commons-io to guava
Added warnings about the borked REST API (#47)

For further details, please see:
https://github.com/davemckain/qtiworks/issues/47