Batch build script

[teverett]

This commit adds "batchbuild.sh" which builds every board on the source tree against a given FreeBSD branch.

Specific changes include:

• Addition of batchbuild.sh
• Addition of "-g" option to crochet.sh to enable autodownloading of u-boot sources and to autoinstall u-boot packages
• Addition of /batch directory containing the config.sh to be used for batch builds
• Addition of ALIX11 configuration to compile Alix boards against FreeBSD 11
• Addition of "-s" option to crochet.sh to enable pointing to a source tree via the command line
• Changes to uboot.sh to enable autodownloading u-boot sources and autoinstalling u-boot packages