Merge branch 'martin-t/shield' into 'master'

Make shield reduce force as well (unless selfpush)

See merge request xonotic/xonotic-data.pk3dir!526

diff --cc balance-mario.cfg
Simple merge

diff --cc balance-nexuiz25.cfg
Simple merge

diff --cc balance-overkill.cfg
Simple merge

diff --cc balance-samual.cfg
Simple merge

diff --cc balance-xdf.cfg
Simple merge

diff --cc balance-xonotic.cfg
Simple merge

diff --cc balance-xpm.cfg
Simple merge

diff --cc qcsrc/server/autocvars.qh
Simple merge