Changes

Summary

1. Improve unresolved variable error message and tests (commit: b301b64) (details)

Commit b301b646a4a90296ba309d30bfffe5d17b5dfbbe by nick.battle Improve unresolved variable error message and tests (commit: b301b64)
	core/typechecker/src/test/resources/Type_Check_SL_Modules_TestSuite_External/fulltest/SL/modules17/modules17.vdm.result (diff)
	core/typechecker/src/main/java/org/overture/typechecker/visitor/AbstractTypeCheckVisitor.java (diff)
	core/typechecker/src/test/resources/Type_Check_SL_Modules_TestSuite_External/exprtest/CORE/expr/casesexpr/casesexpr-01.vdm.result (diff)
	core/typechecker/src/test/resources/Type_Check_SL_Modules_TestSuite_External/fulltest/CORE/stmt/letbestmt/letbestmt.vdm.result (diff)
	core/typechecker/src/test/resources/Type_Check_SL_Modules_TestSuite_External/fulltest/SL/opdef/opdef.vdm.result (diff)
	core/typechecker/src/main/java/org/overture/typechecker/ModuleEnvironment.java (diff)
	core/typechecker/src/main/java/org/overture/typechecker/utilities/type/PTypeResolver.java (diff)
	core/testing/samples/src/test/resources/external/cgip/sltest/CORE/types/types-04.vdm.result (diff)
	core/typechecker/src/test/resources/Type_Check_SL_Modules_TestSuite_External/fulltest/CORE/stmt/casesstmt/casesstmt-01.vdm.result (diff)
	core/typechecker/src/test/resources/Type_Check_SL_Modules_TestSuite_External/exprtest/CORE/expr/casesexpr/casesexpr-03.vdm.result (diff)
	core/typechecker/src/test/resources/Type_Check_SL_Modules_TestSuite_External/fulltest/SL/stmtsl/rectrapstmt/rectrapstmt.vdm.result (diff)
	core/typechecker/src/test/resources/Type_Check_SL_Modules_TestSuite_External/fulltest/CORE/stmt/blockstmt/blockstmt.vdm.result (diff)
	core/testing/samples/src/test/resources/external/tc/sltest/exprtest/CORE/expr/setcomprehensionexpr/setcomprehensionexpr-07.vdm.result (diff)
	core/typechecker/src/main/java/org/overture/typechecker/visitor/TypeCheckerExpVisitor.java (diff)
	core/testing/samples/src/test/resources/external/tc/sltest/fulltest/CORE/stmt/blockstmt/blockstmt.vdm.result (diff)
	core/testing/samples/src/test/resources/external/cgip/sltest/CORE/stmt/assignstmt/assignstmt-21.vdm.result (diff)
	core/typechecker/src/test/resources/Type_Check_SL_Modules_TestSuite_External/exprtest/CORE/expr/setcomprehensionexpr/setcomprehensionexpr-07.vdm.result (diff)
	core/testing/samples/src/test/resources/external/cgip/sltest/CORE/types/types-06.vdm.result (diff)
	core/testing/samples/src/test/resources/external/tc/sltest/fulltest/SL/modules17/modules17.vdm.result (diff)