Bug fixes for accumulo-mojo (logging, maven cleanup)

I've made some changes to the pom.xml files and the test code, and the maven pom.xml files to fix issues with building due to logging dependencies not being able to be resolved correctly.

The plugin now builds for me, but I don't think it's correct. First, it seems to re-use the same instance id, and that causes an extra, unaccounted-for prompt when Accumulo initializes. Second, the MiniDFSCluster doesn't seem to be used. It still seems to be checking for an initialized Accumulo in my real HDFS instance (even when shut down).

The plugin dependency on hadoop-core, based setting a property doesn't work, and the cdh version of Hadoop isn't available without specifying additional repos (that should be in the pom.xml). The property works when establishing the dependencies for building the plugin, but it doesn't work when using the plugin (as in the tests).