and have more confidence with the unit testing framework.
Now `make testfront` won't retry on failure and testing files are
ordered in each run so that it's possible to reproduce testing failure.
And this patch also fix flush settings not working before suspend issue:
at some point the `FlushSettings` event is sent to `UIManager` instead
of `ReaderUI`, but `UIManager` only delegated events to active widgets
and `ReaderUI` is actually not an active widgets thus will miss the event.
This patch also add a verbose debug mode with "-v" as a switch to turn
on this mode. With verbose mode on, event handling will be logged.
1. It turns out that `device_id` is not defined in unit test environment
which makes the `assert(self.kosync_device_id)` fail and somehow makes `luajit` segmentation fault.
2. In the device spec, stubbing `io.open` will make subsquent `require`
all return boolean value and segmentation fault `luajit`.
This patch is a minimum viable change that makes CI work on both my
local box and Travis.
