Remove debugging print calls

Signed-off-by: martin f. krafft <madduck@madduck.net>
Add optional name attribute to entities

Entities can now carry an optional name attribute, and the YamlFile
class uses that to store the basename of the file, which eases debugging
tremendously.

Signed-off-by: martin f. krafft <madduck@madduck.net>
Fix merging of parameters

The merging logic was wrong, inverting the behaviour of parameter
merging, somewhat anyway.

This is now fixed. Entities are collected in a list, and then the list
is reduced through merging the second element into the first. The entity
of the current level is only merged once, at the very end.

Signed-off-by: martin f. krafft <madduck@madduck.net>