1.1706.0

I've used version 1.2.0 for the bundle spec in case we want to
distinguish between the version that was in the latest release of
this package (1.0.0) and the version that was on docs.apertis.org
at the time 17.03 was released (currently described as 1.0.0, but
1.1.0 would be a better label for it, since it allows <custom>
while 1.0.0 did not). Arguably the bundle spec should also be
using branch-based versioning, which would make it version 1.1706.x,
but let's not go there right now.

Signed-off-by: Simon McVittie <smcv@collabora.com>