The config-repo / project-repo terminology is confusing and we've
generally been using trusted-project and untrusted-project instead.
The term "untrusted-project" is straightforward, but "trusted-project"
is a little misleading, since there are other characteristics which
define it (notably, that the configuration held in it is branchless).
A better term for that might be "config-project".
Since the main config now directly refers to projects rather than
repos, complete the transition by replacing all config-repo
occurances with config-project and likewise project-repo with
untrusted-project.
Change-Id: I2341aa94e3622e2647b0506b78bc84dbcdec1901
Story: 2000953
109da3f9a7