WELD-1413 Fix warning about invalid beans.xml

Actually it's not possible to identify the validation error correctly.
Instead we check SAXParseException#getMessage() to start with "cvc-elt"
code and contain root element name (previously the whole localized
message was matched).
WELD-1317 Fix Tomcat instructions
- also replace org.codehaus.mojo.tomcat-maven-plugin with
org.apache.tomcat.maven plugins (Tomcat 6 and Tomcat 7 version)
- fix several checkstyle warnings
- skip checkstyle for all examples modules
CrossContextInclusionTest (WELD-1415)