Support receiving shared plain text

This will parse the shared text, and add an item for each line
in that text.

This works very well with (for example) the shopping-list feature
of the MyCookbook app.
I think this also fixes the feature request found here:
http://openintents.uservoice.com/forums/86421-general/suggestions/1294309-oi-shopping-list-sms-email-copypaste-import-expor
Extra functionality in widget

I think it is too easy to hit an item and mark it as 'bought' by
accident.  And after it happened, it is difficult to know which item
it was (if you even noticed that this happened).
Therefore I think it is better to display the 'bought' items grayed out,
and have an extra button in the widget to clean the list.
I chose the default 'delete' menu icon, and not the icon as used in
the app, because that one is really difficult to see on the light
widget background.

Also aligned the icons and title text to the top of the widget, because
on a tablet a widget with a large height had the buttons somewhere
in the middle which looks strange
Extract abstract superclass

I want to use the same config app for another widget, but that widget
only supports honeycomb or higher, so should not be referenced from
code that is used by lower android versions.
Therefore I cannot use *exactly* the same config app, but need two
versions.
So this commit extracts most code to a new abstract superclass, and
only the reference to the actual widget class is implemented in the
subclass.
Add widget for honeycomb and higher: using a listview

For older android versions that don't support ListView in
a widget the old widget with pages is kept.
I tested it with a simulator for android 2.3.1.  I verified that
indeed the old widget is shown, but I must say that not all
functionality worked there.  The 'next page' button didn't go
to the next page, and marking an item as finished didn't work
either.  I did the same tests with the master branch, and they
failed there as well, so I think my code didn't break anything
that was not already broken.