Added build commands for various versions of Visual Studio

- For people who want to build the library without opening it in VS

build/build.VS2015.cmd

@@ -0,0 +1,7 @@
+@echo off
+
+rem build 32-bit
+call "%~p0%build.generic.cmd" VS2015 Release "Clean,Build" Win32 v140
+
+rem build 64-bit
+call "%~p0%build.generic.cmd" VS2015 Release "Clean,Build" x64 v140