Update documentation on job level build variables
Update documentation on job level build variables

SVArago/gitlabhq,stoplightio/gitlabhq,LUMC/gitlabhq,axilleas/gitlabhq,larryli/gitlabhq,mr-dxdy/gitlabhq,SVArago/gitlabhq,screenpages/gitlabhq,daiyu/gitlab-zh,dwrensha/gitlabhq,mr-dxdy/gitlabhq,martijnvermaat/gitlabhq,icedwater/gitlabhq,iiet/iiet-git,mr-dxdy/gitlabhq,openwide-java/gitlabhq,icedwater/gitlabhq,dreampet/gitlab,jirutka/gitlabhq,darkrasid/gitlabhq,shinexiao/gitlabhq,stoplightio/gitlabhq,t-zuehlsdorff/gitlabhq,darkrasid/gitlabhq,SVArago/gitlabhq,daiyu/gitlab-zh,dwrensha/gitlabhq,darkrasid/gitlabhq,screenpages/gitlabhq,dreampet/gitlab,stoplightio/gitlabhq,shinexiao/gitlabhq,openwide-java/gitlabhq,allysonbarros/gitlabhq,LUMC/gitlabhq,martijnvermaat/gitlabhq,LUMC/gitlabhq,allysonbarros/gitlabhq,larryli/gitlabhq,axilleas/gitlabhq,dwrensha/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq,htve/GitlabForChinese,shinexiao/gitlabhq,axilleas/gitlabhq,dreampet/gitlab,daiyu/gitlab-zh,martijnvermaat/gitlabhq,t-zuehlsdorff/gitlabhq,jirutka/gitlabhq,daiyu/gitlab-zh,SVArago/gitlabhq,mr-dxdy/gitlabhq,dplarson/gitlabhq,dplarson/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,icedwater/gitlabhq,dreampet/gitlab,shinexiao/gitlabhq,iiet/iiet-git,dwrensha/gitlabhq,htve/GitlabForChinese,axilleas/gitlabhq,dplarson/gitlabhq,openwide-java/gitlabhq,mmkassem/gitlabhq,t-zuehlsdorff/gitlabhq,t-zuehlsdorff/gitlabhq,jirutka/gitlabhq,allysonbarros/gitlabhq,martijnvermaat/gitlabhq,allysonbarros/gitlabhq,Soullivaneuh/gitlabhq,screenpages/gitlabhq,Soullivaneuh/gitlabhq,openwide-java/gitlabhq,Soullivaneuh/gitlabhq,iiet/iiet-git,htve/GitlabForChinese,larryli/gitlabhq,iiet/iiet-git,darkrasid/gitlabhq,Soullivaneuh/gitlabhq,htve/GitlabForChinese,screenpages/gitlabhq,dplarson/gitlabhq,LUMC/gitlabhq,larryli/gitlabhq,icedwater/gitlabhq,jirutka/gitlabhq