Implement glob matching for `include:` directive

Knot DNS supports include directive that could either include file or full directory.

However the directory include has a slight problem - it will include all files in the directory including:

file~
file.bak
file.old
file.dpkg-orig
file.dpkg-dist
file.ucf-orig
...
and all other stuff people use instead of versioning :)

We could probably skip the most obvious ones, e.g. '*~', but better solution would be to include proper glob support in the include directive, and then one could do:

include: "/etc/knot/knot.conf.d/*.conf"

and magically solving all of those problems.