ACCUMULO-1419 Update README, confs and poms to switch default hadoop
dependency to 2.2.0.

Document the change in default Apache Hadoop dependency. Update
configurations to account for new HADOOP_CONF_DIR and hadoop-2 classpath
entries. Rename profiles from hadoop-1.0 to hadoop-1.2 and hadoop-2.0 to
hadoop-2.2, along with updated dependencies for the hadoop-2.2 profile.