GTNPORTAL-3400 - Added encodeIfNotEncoded

- Added a new method on the HTMLEntityEncoder, to encode an input only if it's not encoded already.
- Changed the UIPortalApplication.gtmpl to use the new encodeIfNotEncoded method, as this is a place that can receive both encoded (like in the Dashboard's title) and non-encoded (like in a page's title) content.

*Important*: this depends on the recently added reverse() method from EntityEncoder, located in gatein-common, so, there's an update also to the pom.xml file. This means that this feature can only be merged once the change on gatein-common is merged and released. When this happens, the version in this pom.xml should be the same, but without the "-SNAPSHOT" suffix.