report: add report_init_for_selection fn and modify report_object to support reportin...

report: add report_init_for_selection fn and modify report_object to support reporting for selection only

The new "report_init_for_selection" is just a wrapper over
dm_report_init_with_selection that initializes reporting for selection
only. This means we're not going to do the actual reporting to output
for display and as such we intialize reporting as if no fields are reported
or sorted. The only fields "reported" are taken from the selection criteria
string and all such fields are marked as hidden automatically (FLD_HIDDEN flag).
These fields are used solely for selection criteria matching.

Also, modify existing report_object function that was used for reporting to
output for display. Now, it can either cause reporting to output or reporting
for selection only. The selection result is stored in struct selection_handle's
"selected" variable which can be handled further by any report_object caller.