syntaxtree, class Node: XML-output now puts tags and content of the innermost node on one line for better readability

- better syntaxtree.mock_syntax_tree() generation: Can now read actual ASTs in S-expression form. Useful for testing of AST-transformation or -validation as long as these do not call isinstance() on any parser.

- Grammar class now defines left und right default white space handling, so it is usually not necessary any more to specify whitespacehandling in the constructor of RE- and Token-objects.

- additions to AST-transformation-table of MLW_compiler.py

- some smaller bugs fixed