WELD-1638 EE7-related doc and example updates

* updated old namespace http://java.sun.com to http://xmlns.jcp.org in doc and examples
* DOC:
 * added a short explanation of "JSR-299" and "JSR-346"
 * replaced EE6-spec mentions with EE7 ones (where it made sense)
 * updated a couple of outdated links (Seam, and DS "incubator")
* EXAMPLES:
 * updated maven-ear-plugin to 2.9 to allow <version>7</version>
 * updated <ejbVersion> to 3.2