Support Yocto license expressions syntax

[pombredanne]

Based on https://github.com/openembedded/openembedded-core/blob/14241ed09f9ed317045cf75a6d08416d3579bb8d/meta/lib/oe/license.py#L217 and https://www.openembedded.org/wiki/Recipe_License_Fields these are license symbols using & for AND and | for OR which should be supported most likely mostly out of the box. See also:

• https://docs.yoctoproject.org/singleindex.html#maintaining-open-source-license-compliance-during-your-product-s-lifecycle
• https://wiki.yoctoproject.org/wiki/License_Infrastructure_Interest_Group
• https://docs.yoctoproject.org/singleindex.html#term-LICENSE
• https://docs.yoctoproject.org/singleindex.html#term-LIC_FILES_CHKSUM
• https://docs.yoctoproject.org/singleindex.html#tracking-license-changes
• https://docs.yoctoproject.org/singleindex.html#maintaining-open-source-license-compliance-during-your-product-s-lifecycle

[pombredanne]

@priv-kweihmann @rpurdie FYI this future update may be of some interest to you.