Removing the contributor documentation from the default build targets

[Pasi Lallinaho]

Hello documentation zealots,

here's a brief summary of a discussion [1] on the IRC channel today:
- The user and contributor documentation are tracked on the same branch 
because they have many common assets
- The user and contributor documentation are however very different in 
nature; the former is and needs to be release-specific and the latter is 
never release-specific

That said, I would like to propose the following:
- While keeping both documentation sources in the same branch, drop 
contributor documentation from the default build target, thus, not 
shipping it with the built documentation on the ISO
- As a consequence of the above, a slight content change needs to be 
done for the start page to point to the online documentation (I can take 
this item)
- The contributor documentation can then be changed when needed and 
docs.xubuntu.org updated with it, without explicitly requiring an upload 
for the package.
- Since the contributor documentation would still be available in the 
source package, make sure the source has a note pointing to the newest 
branch in case somebody wants to build the contributor documentation (I 
can take this item too)

Technically, this is only a slight change and we can fortunately keep on 
using the current Makefiles and build scripts.

Any comments? Agree or disagree?

Cheers,
Pasi

[1] Starting from 
http://irclogs.ubuntu.com/2016/03/18/%23xubuntu-devel.html#t21:19

-- 
Pasi Lallinaho (knome)                » http://open.knome.fi/
Leader of Shimmer Project             » http://shimmerproject.org/
Ubuntu member, Xubuntu Website Lead   » http://xubuntu.org/