Support network images in ReadThreadActivity

This enables viewing emoticons and displaying of new-style attached
images. Old-style attachments are not supported for now because the
PHP-end mandates several cookies.

The implementation, based on answers to a couple of StackOverflow
questions, uses AsyncTask. Next it will be migrated to RoboSpice for
better consistency throughout the app.
add diagnose commands to track paths
print more directory info
make the sdk directory 0755
remove $PATH display
Fix: ~/builds changed to ~/build. Oh well.
typo: platform_tools -> platform-tools
no platform-tools? seems I missed some changelog items...
still no platform-tools...

Let's see what happened to the SDK after installing...
see what is inside platform-tools/
maybe stale hashes is the reason, so flush them
(Hopefully) eventually fix .travis.yml

... with information provided in
http://rkistner.github.com/android/2013/02/05/android-builds-on-travis-ci/
some conf migration choice has to be answered

Just use the default, since the affected conf file (/etc/mysql/my.cnf)
is not used by our project.
Merge branch 'fix-travis-yml'
Merge branch 'add-url-image-support'
add forgotten license header
Merge branch 'fix-license'