org.el: New command `org-set-property-and-value' bound to `C-c C-x P'

org.el: New command `org-set-property-and-value' bound to `C-c C-x P'

* org.el (org-last-set-property-value): New variable.
(org-read-property-name): Fix dangling parentheses.
(org-set-property-and-value): New command to manually set
both the property and the value.  A prefix arg will use the
last property-value pair set without prompting the user.
(org-set-property): Set `org-last-set-property-value'.
(org-mode-map): Bind the new command to `C-c C-x P'.

This is useful when you need to set the same property-value
pair for several entries.