updating the screen in tap handler of readerfooter is not needed

Was a hack anyway, c.f.
https://github.com/koreader/koreader/pull/1306#discussion_r21057461

Seems to be not needed anymore. If some areas are now not refreshed
anymore, that ought to be fixed in another place.

This also gets rid of redundant screen flashes.
on finish of pan gesture when scrolling, do partial refresh

it was set to a full refresh. However, we want to behave as if in
non-scrolling mode and issue a partial refresh. That might get
updated to a full refresh if the full-refresh counter has reached
the limit - which is configurable.
fix dict window refresh

was still using old API
also, move this to another place.
Merge pull request #1312 from Frenzie/master

OPDS: refactored unit test and fixed a minor bug with undefined image_rel
allow for more control on refreshes when show()ing widgets

for now, we have show() automatically call setDirty() for the new
widget, as before. However, now show() takes two arguments for
refresh configuration that will get passed on to setDirty().

For compatibility, the default is here in show() to do a partial
refresh. So if you want no refresh triggered (via this show() call),
add a function that doesn't return anything.
dictionary window triggers refresh itself, not via show()
record ButtonDialog.dimen
refresh only dialog part of the screen for multi-word selection window
add refresh control to UIManager:close()
use API for refresh when closing widgets in message popups
Merge pull request #1310 from hwhw/master

fixes for scrolling, fix for double-refresh, misc stuff
make coverage in after_success stage
So that if the coverage job is timeout it won't fail the
CI result.
fix coverage test fails on OPDS browser module
for some reason luxl.lua has problem when being set hook for luacov
fix #1175
Merge pull request #1314 from chrox/master

make coverage in after_success stage
small change of UIManager:show(): No more automatic refresh

This eliminates the API difference between the extra parameters of
UIManager:show() and setDirty(). They work the same now.
Note that this also eliminates the automatic refresh that took place
before when using show() without refresh options. It always refreshed
the full screen, which led to too big refresh regions all over the
place. Thus, refresh has now explicitly to be asked for, hopefully
encouraging to implement it in the widget that gets shown (and is
aware about the screen region it covers).

Also add an event that is triggered when a widget is closed:
CloseWidget. So a widget can implement "onCloseWidget()" to trigger
actions upon closing - most commonly, this is a refresh for the area
previously taken by the widget. That way, the widget's user does not
have to take measures to ensure that the area is refreshed later.
clean up refreshes

This is a larger clean-up of the refresh situation.
The general shift is that refreshes are now mainly triggered by
the (top-level) widgets when they get shown or closed via UIManager.

All refreshes for the widgets when they are in use were handled by
themselves before. This adds the case of showing/closing.

It is the desired result of not having UIManager:show()/:close()
do (full screen) refreshes on its own.
UIManager:_refresh(): no more default refresh

If no refresh type is specified, don't do a refresh.
There should be now refresh types specified in all relevant places.
fix widget closing
Merge pull request #1316 from hwhw/master

killling/shrinking refreshes