tree.js: rename getDsKeyByVersion to _getDsKeyByVersion
tree.js: rename getDsKeyByVersion to _getDsKeyByVersion

Netsend/persdb,Netsend/PerspectiveDB,Netsend/persdb,Netsend/mastersync,Netsend/PerspectiveDB,Netsend/persdb,Netsend/PerspectiveDB,Netsend/mastersync,Netsend/mastersync