documentation.conf (LICENSE): tiny addition

Examples:

LICENSE = "MIT"
LICENSE = "GPLv2 & LGPLv2.1"
LICENSE = "AFL-2 | GPLv2+"
LICENSE = "MIT & BSD-3-Clause & BSD-2-Clause & PD"
LICENSE = "GPLv2 & (LGPLv2.1 | MPL-1.1 | BSD)"
LICENSE = "GPLv2+ & LGPLv2+ & ( (GPLv2+ & LGPLv2.1+) | (GPLv3+ & LGPLv3+) )"

Signed-off-by: Matthieu Crapet <Matthieu.Crapet@ingenico.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
toaster.bbclass: image file is missing a "/"

Relaced the key with the join between path and file name.

[YOCTO #6090]
Signed-off-by: Cristiana Voicu <cristiana.voicu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
package.bbclass: Add CONFFILES to list of package specific variables

Changes to CONFFILES should change the sstate checksum. To make that happen,
it needs to be listed in the list of package specific variables, therefore
add it.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>