split Cell2DS and JavaBackendCell2DS properly; fixed JavaBackendCell2DS
fixed RewriteEngineUtils#evaluateConditions
fixed side condition evaluation properly
added some comment
added defensive code for concatenating two maps with common keys
relaxed the check of AC-Matching to be more accurate
fixed ConstrainedTerm#unify; added defensive code to check unsplit disjuctions
excluded rules with AC-matching in side-conditions from fast rewriting; added TODO comment
remove static state in JavaClassesFactory
localize sdf to a single definition
make conses thread safe
fix repeated injection of expensive operations in krun
added regression test
Merge pull request #1117 from dwightguth/javaclasses

remove static state in JavaClassesFactory
add javadoc
fix failure to report errors
fix Radu's comment
Merge pull request #1120 from dwightguth/singleton

fix repeated injection of expensive operations in krun
Merge pull request #1114 from yilongli/fix-java-backend

Fix java backend
file io refactoring