Proper logging prefix for ext_pillar errors

Signed-off-by: martin f. krafft <madduck@madduck.net>
Allow reclass source path to be specified in master config

Since __virtual__ also gets __opts__, it is possible to conditionally
prepend a path defined in the master config file to the module search
path before looking for the 'reclass' module.

Signed-off-by: martin f. krafft <madduck@madduck.net>
Initialise inventory_base_uri to the first file_roots of class 'base'

If inventory_base_uri was not provided in the reclass configuration in
the Salt master config file, and there is a file_roots of class 'base'
configured, then default the inventory_base_uri to that directory.

Signed-off-by: martin f. krafft <madduck@madduck.net>
Merge pull request #5952 from madduck/reclass-adapter_improvements

Reclass adapter improvements