much more sane rules for sequence, unneeded InstructionSequences removed
made RenderInstruction width optional
fixed incorrect optimizations for sequence and sequence_group

only omit wrapping the nodes in InstructionSequences if they
already are InstructionSequences, otherwise we can not guarantee
scoping for ECIs as well as that we will have a InstructionSequences
as the root of the output
organized & renamend parser tests
made RenderInstruction default simpler
made use of RenderInstruction defaults in tests
fixed handling of lowercase letters