Revamping the FlatBuffers docs.

Adding an API reference for the supported languages.

General docs cleanup, including a new `tutorial` section that
supports all of the supported languages.

Added samples for each supported language to mirror the new
tutorial page.

Cleaned up all the links by making them `@ref` style links,
instead of referencing the names of the generated `.html` files.

Removed all generated files that were unnecessarily committed.

Also fixed the C# tests (two were failing due to a missing file).

Bug: b/25801305

Tested: Tested all samples on Ubuntu, Mac, and Android. Docs were
generated using doxygen and viewed on Chrome.

Change-Id: I2acaba6e332a15ae2deff5f26a4a25da7bd2c954

samples/android/res/values/strings.xml

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) 2015 Google, Inc.
+
+     This software is provided 'as-is', without any express or implied
+     warranty.  In no event will the authors be held liable for any damages
+     arising from the use of this software.
+     Permission is granted to anyone to use this software for any purpose,
+     including commercial applications, and to alter it and redistribute it
+     freely, subject to the following restrictions:
+     1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+     2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+     3. This notice may not be removed or altered from any source distribution.
+ -->
+<resources>
+    <string name="app_name">FlatBufferSample</string>
+</resources>