Added Initial Tomcat 7 Support

Here is some initial work to add Tomcat 7 support.  It is not complete.  In particular it doesn't yet support customConf files/xml.  It also puts Tomcats working files in the root directory of your project rather than in the 'target' directory.   To fix this would require a slight API change so the Runners know where the 'target' directory is.  Alternately, Tomcat could just be configured to put its stuff in a temp directory (although then 'clean' might not work as expected'.

Also, I haven't written any tests yet.  I wasn't sure if I should just add to the existing tests because the seem very manual.  Maybe some work should going in to making them more automated.  Let me know and I will add tests wherever. 

To use Tomcat in a project you just need add the dependencies:

```
libraryDependencies ++= Seq(
    "org.apache.tomcat.embed" % "tomcat-embed-core" % "7.0.22" % "container",
    "org.apache.tomcat.embed" % "tomcat-embed-logging-juli" % "7.0.22" % "container",
    "org.apache.tomcat.embed" % "tomcat-embed-jasper" % "7.0.22" % "container",
    "org.eclipse.jdt.core.compiler" % "ecj" % "4.2.1" % "container"
)
```
The 'eclipse' dependency is not necessary if you are not using JSPs.