[Bf-committers] Enabling Try scheduler on our Buildbot

[Bastien Montagne]

Being able to build in "release conditions" WIP development would be a 
great enhancement to get early testing.

With buildbot, we can achieve this in two ways (not exclusive):

* Enable extra branches building (this is rather simple actually, using 
the ForceScheduler);

* Enable patch-building, using one of the two available Try schedulers.

There are two versions of the Try schedulers 
(http://docs.buildbot.net/0.8.8/manual/cfg-schedulers.html#try-schedulers), 
one that enable users by login/password directly in config of master, 
the other needs a directory shared by all devs having access to this 
feature (which mean those devs need an account on the master server).

Allowed devs can then use buildbot command line tool to send patches to 
the master.

We need our buildbot maintainer (Sergey) and server administrators' 
advice about security stuff implied by this Try scheduler (we obviously 
can't put passwords in clear in master.cfg if we share it in our git 
repo! :P ).

Cheers,
Bastien.