[sr-dev] mtree module issues

[Juha Heinanen]

mtree module still has a few issues:

- parameters mt_allow_duplicates/mt_ignore_duplicates seem to have global
  meaning affecting all mtrees.

- if db_table module param is used instead of mtree module params, all
  trees in the table must have either int or string values

my suggestion is that in the future db_table module param is removed and
all relevant other module parameters is moved to parameters of mtree
module parameter.

-- juha