extend Cut #41

I'd like to propose two extensions for the Cut (;.) dyad.

Some partitioned algorithms require to have position of non-complete shard at the begin of array. Current u;.3 and u;._3 implementation provides that shard at the end of array only. Following is the model of extension desired ("5" is selected randomly for example only):

   (4 ,: 3) <;.5 (i. 10)
┌───┬─────┬─────┐
│0 1│2 3 4│6 7 8│
└───┴─────┴─────┘

Sometimes there is a need to align selected shard within frame not to the left (beginning) of the frame as currently implemented, but to the right (end), too:

   (_4 ,: 3) <;.3 (i. 10)
┌─────┬─────┬───┐
│1 2 3│5 6 7│8 9│
└─────┴─────┴───┘
   (_4 ,: 3) <;.5 (i. 10)
┌───┬─────┬─────┐
│0 1│3 4 5│7 8 9│
└───┴─────┴─────┘

-- Igor Zhuravlov <2009-12-26T16:55:18Z)>