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/shell.go

@@ -0,0 +1,7 @@
+package token
+
+// OpenBrowser opens the specified URL in the default browser of the user
+func OpenBrowser(url string) error {
+	return getBrowserCmd(url).Start()
+}
+