Restructure object model to similar to the other SOMs

- rename classes to use 'S' prefix, which avoids name clashes with java.lang
- rename SObject to SAbstractObject (will introduce a SObject again in next step)

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Added BasicInterpreterTests from TruffleSOM

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Use simple instead of fully qualified names

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Removed SymbolTable

File removal was already committed unfortunately.
Don't need it, will just use hash map directly

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Moved Frame to interpreter package

It is implementation specific, and no longer handled as a VMObject. A previous commit did already part of this.

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Make VM objects, immutable, and proper abstract objects where useful

- SSymbol is now a subclass of SString
- removed dead code from SMethod
- removed dead code from SClass (replaceBytecode)
- getSOMClass now requires the universe as parameter

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Added missing primitives for Class,  Method, and Primitive

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Updated to latests core-lib

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Added Universe.current() and some minor cleanups

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Refactored interpreter startup for BasicInterpreterTests

Interpreter now returns top-of-stack with the halt-bytecode

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Fix parser to support direct access to superclass fields

The class generation context now knows the fields of the super class.

Signed-off-by: Stefan Marr <git@stefan-marr.de>