add exists function to manual
add exists function to manual

Signed-off-by: John Thornton <601166b5efca3d35ab1942428a84fb6f8bcae6cc@gnipsel.com>

ArcEye/MK-Qt5,ArcEye/machinekit-testing,cnc-club/linuxcnc,cdsteinkuehler/linuxcnc,ikcalB/linuxcnc-mirror,kinsamanka/machinekit,cdsteinkuehler/linuxcnc,ikcalB/linuxcnc-mirror,ianmcmahon/linuxcnc-mirror,araisrobo/linuxcnc,cdsteinkuehler/linuxcnc,Cid427/machinekit,unseenlaser/linuxcnc,cdsteinkuehler/MachineKit,ArcEye/MK-Qt5,bmwiedemann/linuxcnc-mirror,ikcalB/linuxcnc-mirror,jaguarcat79/ILC-with-LinuxCNC,araisrobo/machinekit,strahlex/machinekit,narogon/linuxcnc,bmwiedemann/linuxcnc-mirror,unseenlaser/linuxcnc,kinsamanka/machinekit,araisrobo/linuxcnc,ikcalB/linuxcnc-mirror,kinsamanka/machinekit,ikcalB/linuxcnc-mirror,kinsamanka/machinekit,strahlex/machinekit,ArcEye/machinekit-testing,narogon/linuxcnc,aschiffler/linuxcnc,EqAfrica/machinekit,bmwiedemann/linuxcnc-mirror,bobvanderlinden/machinekit,RunningLight/machinekit,narogon/linuxcnc,ArcEye/MK-Qt5,kinsamanka/machinekit,bobvanderlinden/machinekit,Cid427/machinekit,aschiffler/linuxcnc,mhaberler/machinekit,ArcEye/machinekit-testing,araisrobo/machinekit,ArcEye/machinekit-testing,araisrobo/machinekit,Cid427/machinekit,araisrobo/machinekit,ianmcmahon/linuxcnc-mirror,EqAfrica/machinekit,unseenlaser/machinekit,EqAfrica/machinekit,strahlex/machinekit,ArcEye/MK-Qt5,strahlex/machinekit,Cid427/machinekit,aschiffler/linuxcnc,mhaberler/machinekit,bobvanderlinden/machinekit,jaguarcat79/ILC-with-LinuxCNC,araisrobo/linuxcnc,Cid427/machinekit,ArcEye/machinekit-testing,kinsamanka/machinekit,RunningLight/machinekit,araisrobo/machinekit,kinsamanka/machinekit,mhaberler/machinekit,mhaberler/machinekit,ianmcmahon/linuxcnc-mirror,jaguarcat79/ILC-with-LinuxCNC,Cid427/machinekit,ianmcmahon/linuxcnc-mirror,jaguarcat79/ILC-with-LinuxCNC,araisrobo/machinekit,cdsteinkuehler/linuxcnc,RunningLight/machinekit,EqAfrica/machinekit,unseenlaser/linuxcnc,strahlex/machinekit,strahlex/machinekit,ikcalB/linuxcnc-mirror,Cid427/machinekit,Cid427/machinekit,cnc-club/linuxcnc,ArcEye/machinekit-testing,ArcEye/MK-Qt5,RunningLight/machinekit,unseenlaser/machinekit,bmwiedemann/linuxcnc-mirror,cnc-club/linuxcnc,unseenlaser/machinekit,cdsteinkuehler/MachineKit,ianmcmahon/linuxcnc-mirror,unseenlaser/machinekit,ArcEye/machinekit-testing,bobvanderlinden/machinekit,narogon/linuxcnc,unseenlaser/machinekit,EqAfrica/machinekit,mhaberler/machinekit,ArcEye/MK-Qt5,unseenlaser/machinekit,ikcalB/linuxcnc-mirror,aschiffler/linuxcnc,unseenlaser/machinekit,unseenlaser/machinekit,bmwiedemann/linuxcnc-mirror,araisrobo/linuxcnc,cdsteinkuehler/MachineKit,cnc-club/linuxcnc,bmwiedemann/linuxcnc-mirror,bmwiedemann/linuxcnc-mirror,aschiffler/linuxcnc,cdsteinkuehler/MachineKit,ArcEye/machinekit-testing,EqAfrica/machinekit,araisrobo/machinekit,unseenlaser/linuxcnc,strahlex/machinekit,araisrobo/machinekit,cdsteinkuehler/linuxcnc,narogon/linuxcnc,ianmcmahon/linuxcnc-mirror,araisrobo/linuxcnc,bobvanderlinden/machinekit,kinsamanka/machinekit,mhaberler/machinekit,ianmcmahon/linuxcnc-mirror,ArcEye/MK-Qt5,cnc-club/linuxcnc,ArcEye/MK-Qt5,cdsteinkuehler/MachineKit,RunningLight/machinekit,bobvanderlinden/machinekit,bobvanderlinden/machinekit,cdsteinkuehler/linuxcnc,araisrobo/machinekit,cdsteinkuehler/MachineKit,RunningLight/machinekit,cnc-club/linuxcnc,unseenlaser/linuxcnc,mhaberler/machinekit,bobvanderlinden/machinekit,RunningLight/machinekit,cnc-club/linuxcnc,RunningLight/machinekit,jaguarcat79/ILC-with-LinuxCNC,EqAfrica/machinekit,mhaberler/machinekit,EqAfrica/machinekit