Introduce StreamIndex to clean up code
Add conjuctive and disjunctive expr visitors
Add Program and Node builders
Merge branch 'master' into function

Conflicts:
	jkind-common/src/jkind/lustre/Program.java
	jkind/src/jkind/analysis/ConstantAnalyzer.java
	jkind/src/jkind/interval/ModelGeneralizer.java
	jkind/src/jkind/processes/Director.java
	jkind/src/jkind/sexp/Cons.java
	jkind/src/jkind/translation/InlineNodeCalls.java
	jkind/src/jkind/util/SexpUtil.java