Add patches and deleting boundary cell ability to delete operator

This MR improves the current polygon session delete operator in three ways:

1. Ability to delete target edge and related vertices at the same time. (In the past we never check this condition)
2. Ability to delete cells and their boundary model entities when they are not used by other cells.
3. Improve the operator option names and their description, easier for the user to understand.

A test case is added.

Close #130 (closed) #106 (closed)

Cc @bob.obara