Extract SVM from Traverser

[sergeypospelov]

Description

Now Traverser contains not only methods for a Jimple traversal, but also methods for working with a SymbolicState. We should define a convenient API for working with SymbolicState and extract all existing methods from Traverser.

Most likely we will need to define new class SVMContext which encapsulates all the necessary information for working with SymbolicState.

Expected behavior

• A convenient SVM API is designed and implemented.
• Methods from Traverser are moved to the new class.
• All usages of these methods (e.g., in wrappers) are refactored.
• Enough documentation is provided.

Potential alternatives

Leave all functions related to SymbolicState in Traverser.kt

Context

See Traverser.kt. See this discussion on refactoring for more information.