TxBridge tests install Arjuna jars into local maven repo which makes troubles when testing on Hudson

The current txbridge tests install Arjuna jars which they depend on to the local maven repo in advance of the test run. This makes troubles on Hudson when more txbridge test jobs are running concurrently.

Remove the install step from build.xml and modify dependencies in pom.xml to use system scope and systemPath for Arjuna bits.