Allow for ignoring other important files

Ignore build, MacOSX and Windows files

Unity.gitignore

@@ -19,3 +19,14 @@
 
 # Unity3D Generated File On Crash Reports
 sysinfo.txt
+
+# Builds
+*.apk
+*.unitypackage
+
+# MacOSX-specific
+.DS_Store
+
+# Windows-specific
+thumbs.db
+