#51 Make DBMS_XPLAN call parameters customizable

[randolf_geist]

DBMS_XPLAN table functions can be used with different parameters for plan output generation.

Currently a hard coded parameter set is used, would be nice to have this configurable (at least) in the "Settings" so one could define his/her own preferred set of parameters (e.g. "peeked_binds" options etc.)