DiaPsRenderer::draw_beziergon (): fix to stroke instead of filling
[substitute] Standard - ZigZagLine: keep points in range
Bug 735303 - Don't create empty groups from VDX

Fixed in the VDX plug-in itself but also on the lib API level
with g_return_val_if_fail (objects != NULL, NULL);
Bug 606377 - Remove static filter list from --filter help string ...

Rather than adding another static string to the dynamic list of export
formats supported add another option. With --list-filters (mentioned
with --help) the list of available filters is created dynamically
fitting the current compilation and configuration.
Implement ShapeRenderer::draw_rounded_rect()

The custom shape module can handle rect with radius for some time. Still
the shape exporter was creating stepwise arc/line shapes with a lot of
superfluous connection points. Now it's just doing the same number of
connection points as the original object (if it was Standard - Box)
custom: fix typos and whitespace usage
custom: restore default to only grow the box with text

Text-fitting was set to ALWAYS but that does not change the behavior
to the better when there is no text.
Make old "Standard - Bus" an alias in sheet, rather than code