Add table of contents, docs on command line args and building for windows

The current readme lacks a table of contents, which makes finding what
you're looking for difficult because of the large amount of images and
text.

The current documentation on building for windows doesn't mention the
fact that package.cmd also has to be run to create a full build. It is
also lacking in other areas, such as the packaging programs required.

The current documentation doesn't reflect the fact that you can pass
command line arguments to the program.

docs/building_for_windows.md

@@ -0,0 +1,34 @@
+# Building for Windows
+
+
+ > * [Requirements](#requirements)
+ > * [Locations and Environment Variables](#locs_and_envs)
+ > * [Building](#features)
+
+<a name="requirements"></a>
+## Requirements
+
+For compiling:
+
+1. Microsoft Visual Studio (tested on 2017 Community)
+2. Qt Framework (tested on 5.10 and 5.11)
+
+Additionally, for fully building portable and installer release versions:
+3. 7zip Command Line
+4. Nullsoft Scriptable Install System (NSIS)
+
+<a name="locs_and_envs"></a>
+## Locations and Environment Variables
+
+Visual Studio must be installed in the default location of `C:\Program Files (x86)\Microsoft Visual Studio\2017\Community`.
+
+The `QT` environment variable must be set to the location of your Qt installation (for example `C:\Qt\5.11.1\msvc2017_64`).
+
+The `PLATFORM` environment variable must be set to `amd64`.
+
+For building the portable and installer release versions, the locations of 7zip Command Line (`7z.exe`) and NSIS (`makensis.exe`) must be in the `PATH` environment variable.
+
+<a name="building"></a>
+## Building
+
+With the programs above installed and environment variables set, go into the root folder of the repository and first run `build_windows.cmd` and then `package.cmd`. Compiled binaries along with everything needed to run portable will output to `.\bin\win64\AdvancedSettings\`.