updates how accumulo version is obtained (#304)

Uses maven to get accumulo version from pom rather than xmllint.  These
changes will work with apache/accumulo#4930

conf/uno.conf

@@ -50,7 +50,7 @@ fi
 # in your workspace and don't want the detected version to change.
 if [[ -n "$ACCUMULO_REPO" ]]; then
   # Detect the version from the accumulo pom.xml in the workspace
-  ACCUMULO_VERSION=$(xmllint --shell "$ACCUMULO_REPO"/pom.xml <<<'xpath /*[local-name()="project"]/*[local-name()="version"]/text()' | grep content= | cut -f2 -d=)
+  ACCUMULO_VERSION=$(mvn -f "$ACCUMULO_REPO/pom.xml" help:evaluate -Dexpression=project.version -q -DforceStdout)
   export ACCUMULO_VERSION
   export ACCUMULO_TARBALL=accumulo-$ACCUMULO_VERSION-bin.tar.gz
 fi