Fix jsf issues

Some issues are raised when sun ri jsf implementation is used without any myfaces library around:

• the default encoding is "application/xhtml+xml" instead of "text/html" because we're taking the sun ri default encoding now that trinidad is not the default render kit.
• the sun ri render kit may not behave the same than trinidad's (responseWriter.writeText can raise a NullPointerException when writing a null text, for instance)
• phase listeners may be registered twice : sun ri implementation differences between 1.2_04 and 1.2_09 has changed, and duplicate phase listeners are not filtered by name anymore (only by listener instance equality) => SeamPhaseListener is registered twice on the same life cycle (and others too)