ADDED: Support setting breakpoints in sweeprolog-mode

ADDED: Support setting breakpoints in sweeprolog-mode

* sweep.pl (sweep_set_breakpoint/2)
(sweep_delete_breakpoint/2)
(sweep_set_breakpoint_condition/2): new predicates.

* sweeprolog.el (sweeprolog-dependency-directive): update
package-version field.
(sweeprolog-set-breakpoint)
(sweeprolog-set-breakpoint-condition)
(sweeprolog-delete-breakpoint)
(sweeprolog-list-breakpoints): new commands.
(sweeprolog-highlight-breakpoints): new user option.
(sweeprolog-mode-map): bind sweeprolog-set-breakpoint.

* README.org (Setting Breakpoints): new manual section.