Consolidated tcp_write() logic in picoTCP driver, updated tcp_closure/tcp_shutdown logic in picoTCP driver, stubbed out more doxygen comments

src/ExampleStackDriver.cpp

@@ -0,0 +1,37 @@
+/*
+ * ZeroTier SDK - Network Virtualization Everywhere
+ * Copyright (C) 2011-2017  ZeroTier, Inc.  https://www.zerotier.com/
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * --
+ *
+ * You can be released from the requirements of the license by purchasing
+ * a commercial license. Buying such a license is mandatory as soon as you
+ * develop commercial closed-source software that incorporates or links
+ * directly against ZeroTier software without disclosing the source code
+ * of your own application.
+ */
+
+
+/*
+
+This file is only meant for those who wish to replace the currently supported network stacks (lwIP and picoTCP) with
+one of their own choosing. If you're looking for information on how to integrate libzt with your application, you 
+should instead go view the (examples) folder. Now let us get started.
+
+ TODO
+
+
+*/