Add JBehave Spring Namespace support for easier configuration

I have implemented an initial version, it is a clone of master branch of jbehave project. My implementation is on git@github.com:maggandalf/jbehave-core.git

Configuring Embedder for working with Spring shall be:

<jbehave:embedder id="embedder">

<jbehave:classpathLoader>target/classes</jbehave:classpathLoader>

<jbehave:output>TXT</jbehave:output>

<jbehave:output>HTML</jbehave:output>

<jbehave:output>CONSOLE</jbehave:output>

</jbehave:embedder>