Enable javadoc 'html' doclint

Also make all 'test' tasks depend on the 'javadoc' task.

Fixes SMACK-650.

smack-extensions/src/main/java/org/jivesoftware/smackx/bookmarks/BookmarkManager.java

@@ -37,7 +37,7 @@ import org.jxmpp.jid.parts.Resourcepart;
 /**
  * Provides methods to manage bookmarks in accordance with XEP-0048. Methods for managing URLs and
  * Conferences are provided.
- * </p>
+ *
  * It should be noted that some extensions have been made to the XEP. There is an attribute on URLs
  * that marks a url as a news feed and also a sub-element can be added to either a URL or conference
  * indicated that it is shared amongst all users on a server.

smack-extensions/src/main/java/org/jivesoftware/smackx/bookmarks/Bookmarks.java

@@ -36,12 +36,10 @@ import org.xmlpull.v1.XmlPullParserException;
  * Bookmark Storage (XEP-0048) defined a protocol for the storage of bookmarks to conference rooms and other entities
  * in a Jabber user's account.
  * See the following code sample for saving Bookmarks:
- * <p/>
  * <pre>
  * XMPPConnection con = new XMPPTCPConnection("jabber.org");
  * con.login("john", "doe");
  * Bookmarks bookmarks = new Bookmarks();
- * <p/>
  * // Bookmark a URL
  * BookmarkedURL url = new BookmarkedURL();
  * url.setName("Google");
@@ -56,8 +54,6 @@ import org.xmlpull.v1.XmlPullParserException;
  * // Save Bookmarks using PrivateDataManager.
  * PrivateDataManager manager = new PrivateDataManager(con);
  * manager.setPrivateData(bookmarks);
- * <p/>
- * <p/>
  * LastActivity activity = LastActivity.getLastActivity(con, "xray@jabber.org");
  * </pre>
  *