Rename JavaValue to Literal
Now return opcode belongs to JavaType itself
Add local type on context
Add load opcode for JavaType
Use JavaType load

Beforea, LocalVaraible use fixed ALOAD only.
Remove commented code
Shorten name: AccessModifier -> Access / JavaVersion -> Java
Make MethodGenerator immutable
Statement list is also immutable
Extract code block abstration Block
Introduce isStatic
Fix bug: this for non-static
Add basic type constants for Object & String
Add Literal.of(String) & test case