Lisp manual improvements for plists and symbol plists.

Lisp manual improvements for plists and symbol plists.

* doc/lispref/commands.texi (Using Interactive): Fix index entry.

* doc/lispref/customize.texi (Variable Definitions):
* doc/lispref/display.texi (Defining Faces):
* doc/lispref/sequences.texi (Char-Tables): Fix xref.

* doc/lispref/lists.texi (Property Lists): Move here from symbols.texi.
(Plist Access): Rename from Other Plists.

* doc/lispref/symbols.texi (Symbol Properties): New node.
(Symbol Plists): Make it a subsection under Symbol Properties.
(Standard Properties): New node.