Don't include BAC in the Linkit core.

BAC (Better autocomplete) is now included in the Linkit core.

Instead it should be added to a .make file and downloaded to the libraries dir.

Tasks to do:

• Add a make file for downloading BAC.
• Add a new (or change the existing) instance to the "linkit_library" with the BAC files.
• Add a description about that Linkit needs BAC in order to work.
• Add a link and description for how to download BAC manually.