Add tomcat8 module to parent pom
Make TomcatBuilder generic, now it manages a configured Embedded/Tomcat instance.

* Made TestUtils generic to return an appropriate TomcatBuilder.
* Moved several tomcat access utils from TestUtils to TomcatBuilder.
* Added EmbeddedTestUtils as replacement for former TestUtils
* Removed duplicated tests from tomcat8 module.

core, tomcat6 and tomcat7 modules are green, tomcat8 now fails with:

Failed tests:
  testContextReload(de.javakaffee.web.msm.MemcachedSessionManagerIntegrationTC8Test): expected:<null> but was:<bar>
  testSerializeSessionFields(de.javakaffee.web.msm.TranscoderServiceTC8Test)
  testSerializeSessionFieldsIncludesFormPrincipalNote(de.javakaffee.web.msm.TranscoderServiceTC8Test)
  testSerializeSessionFieldsIncludesFormRequestNote(de.javakaffee.web.msm.TranscoderServiceTC8Test)
  testSerializeSessionFieldsWithAuthenticatedPrincipal(de.javakaffee.web.msm.TranscoderServiceTC8Test)
  testSerializeSessionWithAttributes(de.javakaffee.web.msm.TranscoderServiceTC8Test)
  testSerializeSessionWithoutAttributes(de.javakaffee.web.msm.TranscoderServiceTC8Test)
  testVersionUpgrade(de.javakaffee.web.msm.TranscoderServiceTC8Test)
  testSessionCreatedForContainerProtectedResourceIsStoredInMemcached(de.javakaffee.web.msm.integration.NonStickySessionsIntegrationTC8Test): expected:<true> but was:<false>
  testFormAuthDontCauseSessionStaleness(de.javakaffee.web.msm.integration.NonStickySessionsIntegrationTC8Test): expected:<true> but was:<false>
  testIgnoredResourcesWithFormAuthDontCauseSessionStaleness(de.javakaffee.web.msm.integration.NonStickySessionsIntegrationTC8Test): expected:<true> but was:<false>
  testSerializationOfAuthStuffWithFormAuth(de.javakaffee.web.msm.integration.TomcatFailoverIntegrationTC8Test): expected:<true> but was:<false>
  testSerializationOfAuthStuffWithFormAuth(de.javakaffee.web.msm.integration.TomcatFailoverIntegrationTC8Test): expected:<true> but was:<false>
Fix TranscoderServiceTC8Test
Fix missing generics in tc8 tests