Filesearcher: added notification for no results
Refactored menu

While looking into #1219 I accidentally ended up refactoring some stuff.

Tested in emulator and on H2O, but be wary because I might have overlooked something.
Fixed spaces stripped out by Transifex in readerui.lua by using util.template
Merge pull request #1227 from Frenzie/master

Fixed spaces stripped out by Transifex in readerui.lua by using util.template
Merge pull request #1226 from Frenzie/filesearcher

Filesearcher: added notification for no results
Merge pull request #1225 from Frenzie/language

Refactored menu
refactor refresh

Lots of the device-related distinction wandered into
base/ffi/framebuffer_<driver>. This eases the refresh logic in
UI manager, which basically only decides what kind of refresh
to trigger. The device specific configuration in the framebuffer
driver decides how to realize that whish.

screen.lua is gone, in its place is now the framebuffer driver.
The device abstraction decides what framebuffer driver to load.
switch from scaleByDPI() to scaleBySize()
update base

pulls the needed changes in base for the refresh refactoring