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).

tools/wbuilder.lua

@@ -129,7 +129,7 @@ Background = InputContainer:new{
     key_events = {
         OpenDialog = { { "Press" } },
         OpenConfirmBox = { { "Del" } },
-        QuitApplication = { { {"Home","Back"} } }
+        QuitApplication = { { { "Home", "Back" } } },
     },
     -- contains a gray rectangular desktop
     FrameContainer:new{