Merge branch 'Mario/minor_fixes' into 'master'

Several fixes for minor issues

Closes #2135, #2360, #2704, #2734, #2749, and #2751

See merge request xonotic/xonotic-data.pk3dir!1095

diff --cc gamemodes-server.cfg
Simple merge

diff --cc qcsrc/common/monsters/sv_monsters.qc
Simple merge

diff --cc qcsrc/server/items/items.qc
Simple merge