nexus-client's file hierarchy overhaul

src/client_exam/utils/go.mod

src/client_exam/utils/utils.go

src/nexus-cli/cmd/Command.go

src/nexus-cli/cmd/go.mod

src/nexus-cli/cmdLogin/go.mod

src/nexus-cli/cmdLogin/login.go

src/nexus-cli/cmdTemplate/go.mod

src/nexus-cli/cmdTemplate/helper.go

src/nexus-cli/cmdTemplate/templateCreate.go

src/nexus-cli/cmdTemplate/templateCreate.go.new

src/nexus-cli/cmdTemplate/templateDel.go

src/nexus-cli/cmdTemplate/templateList.go

src/nexus-cli/cmdUser/go.mod

src/nexus-cli/cmdUser/go.sum

src/nexus-cli/cmdUser/helper.go

src/nexus-cli/cmdUser/userAdd.go

src/nexus-cli/cmdUser/userDel.go

src/nexus-cli/cmdUser/userList.go

src/nexus-cli/cmdUser/userSetCaps.go

src/nexus-cli/cmdUser/userUpdatePwd.go