move reader code into frontend/apps/reader

it makes more sense to completely separate the UI framework and
application code

also move frontend/ui/configurable.lua to frontend/configurable.lua

frontend/apps/reader/modules/readerhinting.lua

@@ -0,0 +1,37 @@
+local EventListener = require("ui/widget/eventlistener")
+
+local ReaderHinting = EventListener:new{
+    hinting_states = {}
+}
+
+function ReaderHinting:onHintPage()
+    if not self.view.hinting then return true end
+    for i=1, DHINTCOUNT do
+        if self.view.state.page + i <= self.ui.document.info.number_of_pages then
+            self.ui.document:hintPage(
+                self.view.state.page + i,
+                self.zoom:getZoom(self.view.state.page + i),
+                self.view.state.rotation,
+                self.view.state.gamma,
+                self.view.render_mode)
+        end
+    end
+    return true
+end
+
+function ReaderHinting:onSetHinting(hinting)
+    self.view.hinting = hinting
+end
+
+function ReaderHinting:onDisableHinting()
+    table.insert(self.hinting_states, self.view.hinting)
+    self.view.hinting = false
+    return true
+end
+
+function ReaderHinting:onRestoreHinting()
+    self.view.hinting = table.remove(self.hinting_states)
+    return true
+end
+
+return ReaderHinting