New window for manage saved views.

 New windows for manage saved views.

Note: Added a pop-up menu with the main operations already avaliable: Save, Rename, Delete and Delete All and a new one: Replace. [Micheus]
It was also added a new feature for "wings_plugins.erl" in order to enable any plugin to save its own window(s) position and custom data.

	modified:   plugins_src/commands/Makefile
	new file:   plugins_src/commands/wpc_views_win.erl
	modified:   src/wings.erl
	modified:   src/wings_plugin.erl