InputContainer: Fall cleanup ;).

Get rid of the doc & seqtext fields, as they are not actually used (nor
are they particularly useful, the event handler's name should be pretty
self-explanatory).

Also, tweak the key_events documentation to highlight the quirks of the
API, especially as far as array nesting is involved...

Random drive-by cleanup of the declarations of key_events & ges_events
to re-use the existing instance object (now that we know they're sane
;p) for tables with a single member (less GC pressure).

frontend/apps/reader/modules/readerconfig.lua

@@ -20,9 +20,7 @@ function ReaderConfig:init()
     self.configurable:loadDefaults(self.options)
 
     if Device:hasKeys() then
-        self.key_events = {
-            ShowConfigMenu = { {{"Press","AA"}}, doc = "show config dialog" },
-        }
+        self.key_events.ShowConfigMenu = { { { "Press", "AA" } } }
     end
     self:initGesListener()
     if G_reader_settings:has("activate_menu") then