Proposal for Lister API: plugin capabilities

[Alextp]

I suggest to give function which Lister plugs can support. Get plugin capabilities. And we have many constants which plugin can set:

ListPluginCap_ is good prefix. Consts:

- plugin supports jump in text by percent 0..100, show % menuitem
- plugin reacts to word wrap menuitem
- plugin reacts to copy/ select-all menuitems
- plugin supports Find (maybe add const for custom Find dialog)
- plugin reacts to Ansi/Ascii enc change
- enable Encodings menu for plugin and give him enc value

!!
- plugin supports Lister window mode
- plugin supports QuickView mode
....etc

If plugin don't have new function, use default set of caps (most values On, only Encodings menu is off).