replace ant build with maven

known issues:
- build and use maven-plugin to build extensions in same reactor, but maven doesn't allowed it.
- most tests doesn't run (currently skipped)
- mixtests for core and webapp in webapp
use github as maven-repository
add travis-ci settings
add travis-ci settings

fix compiler settings and set requiered maven version to 3.0.0
fix travis.yml
add travis ci status 

skip ci
travis status use markdown

skip ci
update classpath for plugins fixes #1
use ziparchiver instead of jararchiver to create extension.zip
use project.build.final name for output files fixes #2
remove necessary parameter in create archiv
use aether to resolve project dependencies fix #3
update dependencies
some smaller code cleanups
fix possible nullpointer in addToClassPath
mark plugin as threadsafe
after update archiver rewritten extension.xml not added to archive
use project.getArtifacts() instead of aether to get all dependencies fix #3

define optional transitiv dependency as direct for inclusion
fix deprecated warning
exclude plexus-utils from maven-project to run under linux

maven-archiver needs a new version (3.0) than maven-projects (1.5) of plexus-utils to run on linux