The library is called MCGL which stands for Minecraft Command Generation Library.
The current version should support all the commands included in Minecraft 1.9 and has some useful additional methods.
MCGL supports exporting the generated commands as a valid *.schematic file for use in mcedit or similar software.
You can check out the Github code here as well as the documentation and additional information here.
Please note, that this version is in a very early state so that there could be some errors I have not noticed yet. Please let me know if you find any. Also please ignore any grammar or spelling mistakes as I am not a native speaker.
I hope some of you find this useful and give me feedback on what to improve or add to it.