contrib: add a basic gitdm config

contrib: add a basic gitdm config

This is a QEMU specific version of a gitdm config for generating
reports on the contributor base of the project. I've added enough
group maps and domain aliases to ensure the current top ten is as
reflective as it can be. As of this commit running:

  git log --numstat --since "Last Year" | gitdm -n -l 10

Reports:

  Top changeset contributors by employer
  Red Hat                   3172 (44.3%)
  Linaro                    1153 (16.1%)
  (None)                     549 (7.7%)
  IBM                        348 (4.9%)
  Academics (various)        170 (2.4%)
  Virtuozzo                  168 (2.3%)
  Wave Computing             118 (1.6%)
  Xilinx                     102 (1.4%)
  Igalia                      93 (1.3%)
  Cadence Design Systems      88 (1.2%)

  Top lines changed by employer
  Red Hat                   144092 (28.1%)
  Cadence Design Systems    126554 (24.6%)
  Linaro                    77480 (15.1%)
  Wave Computing            33134 (6.5%)
  SiFive                    14392 (2.8%)
  IBM                       12219 (2.4%)
  (None)                    11948 (2.3%)
  Academics (various)       10447 (2.0%)
  Virtuozzo                 10445 (2.0%)
  CodeWeavers               9179 (1.8%)

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Aleksandar Markovic <amarkovic@wavecomp.com>