Initial release of the Windows Terminal source code

This commit introduces all of the Windows Terminal and Console Host source,
under the MIT license.

doc/EXCEPTIONS.md

@@ -0,0 +1,36 @@
+# Using Exceptions
+
+## Philosophy
+Introducing exceptions to an existing non-exception-based codebase can be perilous. The console was originally written
+in C at a time when C++ was relatively unused in the Windows operating system. As part of our project to modernize the
+Windows console, we converted to use C++, but still had an aversion to using exception-based error handling in
+our code for fear that it introduce unexpected failures. However, the STL and other libraries like it are so useful that
+sometimes it's significantly simpler to use them. Given that, we have a set of rules that we follow when considering
+exception use.
+
+## Rules
+1. **DO NOT** allow exceptions to leak out of new code into new code
+1. **DO** use NTSTATUS or HRESULT as return values as appropriate
+1. **DO** Encapsulate all exception behaviors within implementing classes
+1. **DO NOT** introduce modern exception throwing code into old code. Instead, refactor as needed to allow encapsulation or
+   use non-exception based code
+1. **DO** use WIL as an alternative for non-throwing modern facilities (e.g. wil::unique_ptr<>)
+
+## Examples
+
+### Encapsulating exception behaviors in a class
+
+    class ExceptionsDoNotLeak
+    {
+        public:
+        HRESULT SomePublicFunction();
+        int iPublic;
+
+        private:
+        void _SomePrivateFunction();
+        int _iPrivate;
+    };
+
+### Using WIL for non-throwing modern facilities
+
+###