Docs: add info on how to calculate base thread for software encoder
Docs: add info on how to calculate base thread for software encoder

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

strahlex/machinekit,kinsamanka/machinekit,araisrobo/machinekit,mhaberler/machinekit,Cid427/machinekit,ArcEye/machinekit-testing,EqAfrica/machinekit,ArcEye/machinekit-testing,bmwiedemann/linuxcnc-mirror,kinsamanka/machinekit,bmwiedemann/linuxcnc-mirror,bmwiedemann/linuxcnc-mirror,RunningLight/machinekit,ikcalB/linuxcnc-mirror,unseenlaser/machinekit,EqAfrica/machinekit,bmwiedemann/linuxcnc-mirror,ArcEye/MK-Qt5,bobvanderlinden/machinekit,mhaberler/machinekit,ArcEye/machinekit-testing,mhaberler/machinekit,ArcEye/machinekit-testing,ikcalB/linuxcnc-mirror,strahlex/machinekit,ikcalB/linuxcnc-mirror,RunningLight/machinekit,kinsamanka/machinekit,ArcEye/machinekit-testing,mhaberler/machinekit,ArcEye/MK-Qt5,kinsamanka/machinekit,strahlex/machinekit,Cid427/machinekit,ikcalB/linuxcnc-mirror,Cid427/machinekit,mhaberler/machinekit,araisrobo/machinekit,kinsamanka/machinekit,RunningLight/machinekit,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,bobvanderlinden/machinekit,Cid427/machinekit,araisrobo/machinekit,ArcEye/MK-Qt5,unseenlaser/machinekit,araisrobo/machinekit,RunningLight/machinekit,EqAfrica/machinekit,unseenlaser/machinekit,jaguarcat79/ILC-with-LinuxCNC,strahlex/machinekit,EqAfrica/machinekit,EqAfrica/machinekit,jaguarcat79/ILC-with-LinuxCNC,ArcEye/MK-Qt5,ArcEye/MK-Qt5,araisrobo/machinekit,ArcEye/MK-Qt5,RunningLight/machinekit,Cid427/machinekit,araisrobo/machinekit,ArcEye/machinekit-testing,bobvanderlinden/machinekit,Cid427/machinekit,kinsamanka/machinekit,bobvanderlinden/machinekit,unseenlaser/machinekit,araisrobo/machinekit,unseenlaser/machinekit,Cid427/machinekit,kinsamanka/machinekit,RunningLight/machinekit,kinsamanka/machinekit,EqAfrica/machinekit,strahlex/machinekit,strahlex/machinekit,mhaberler/machinekit,mhaberler/machinekit,RunningLight/machinekit,mhaberler/machinekit,unseenlaser/machinekit,bobvanderlinden/machinekit,bobvanderlinden/machinekit,strahlex/machinekit,jaguarcat79/ILC-with-LinuxCNC,ArcEye/machinekit-testing,ArcEye/machinekit-testing,bmwiedemann/linuxcnc-mirror,ikcalB/linuxcnc-mirror,bmwiedemann/linuxcnc-mirror,EqAfrica/machinekit,jaguarcat79/ILC-with-LinuxCNC,jaguarcat79/ILC-with-LinuxCNC,araisrobo/machinekit,bmwiedemann/linuxcnc-mirror,araisrobo/machinekit,ArcEye/MK-Qt5,EqAfrica/machinekit,unseenlaser/machinekit,RunningLight/machinekit,bobvanderlinden/machinekit,ArcEye/MK-Qt5,unseenlaser/machinekit,bobvanderlinden/machinekit,Cid427/machinekit