doc, mention API stability

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
doc, add a section explaining the router/dealer programs

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
doc, cosmetics, be generous with vertical whitespace

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>