JBEHAVE-985:  Added asString() method to Step interface and to model objects where missing.

Conflicts:
	jbehave-core/src/main/java/org/jbehave/core/model/Narrative.java
JBEHAVE-976:  Allow specification of resource syntax, defaulting to xwiki/2.0.
JBEHAVE-985:  Added asString() method to Step interface and to model objects where missing.

Conflicts:
	jbehave-core/src/main/java/org/jbehave/core/model/Narrative.java