XLST-Runner and Validator aren't compatible with Java 5

In XSLT-Runner
1. ODFURIResolver.resolve() called String.isEmpty(), which only exists in Java 6. Trivial fix is to test for length() ==0.
2. ODFXSLTRunnner.runXSLT() calls a 2-parameter newInstance() method that exists only in Java 6:
http://docs.oracle.com/javase/6/docs/api/javax/xml/transform/TransformerFactory.html#newInstance%28java.lang.String, java.lang.ClassLoader%29

In Validator
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.3.2:compile (default-compile) on project odfvalidator: Compilation failure
[ERROR] Failure executing javac, but could not parse the error:
[ERROR] javac: invalid flag: -s

caused by:
<configuration>
<source>1.5</source>
<target>1.5</target>
<meminitial>512m</meminitial>
<maxmem>1024m</maxmem>
<showDeprecation>true</showDeprecation>
</configuration>

it was hard-coded to 1.6 before in pom.xml.