Petitboot v1.3.1 & v1.2.6 released

[Samuel Mendoza-Jonas]

Both Petitboot v1.3.1 and v1.2.6 have been tagged with the following commit:
"discover/pxe-parser: Parse only the first config"

This fixes a regression of sorts where Petitboot would parse *every* PXE
config made available to it instead of only the most-suitable first (eg. a
machine specific config over a default config). This could lead to unexpected
autoboot behaviour depending on the contents of each config file.