TUN-4063: Cleanup dependencies between packages.

- Move packages the provide generic functionality (such as config) from `cmd` subtree to top level.
- Remove all dependencies on `cmd` subtree from top level packages.
- Consolidate all code dealing with token generation and transfer to a single cohesive package.

token/launch_browser_windows.go

@@ -0,0 +1,18 @@
+//+build windows
+
+package token
+
+import (
+	"fmt"
+	"os/exec"
+	"syscall"
+)
+
+func getBrowserCmd(url string) *exec.Cmd {
+	cmd := exec.Command("cmd")
+	// CmdLine is only defined when compiling for windows.
+	// Empty string is the cmd proc "Title". Needs to be included because the start command will interpret the first
+	// quoted string as that field and we want to quote the URL.
+	cmd.SysProcAttr = &syscall.SysProcAttr{CmdLine: fmt.Sprintf(`/c start "" "%s"`, url)}
+	return cmd
+}