add more defaults in .XT$.options for DT

[MikeBadescu]

Problem:

looking at createDT notice that only a few settings from $.options are passed to DT::datatable --> the DT table creation is not flexible enough

Solution:

• solve first construct xt Config using several functions #2
• add more default values in .XT$.options ....
• note: start with current values used in createDT