Updated according to comments.

Changed tabs to spaces in AndroidManifest.xml
Using TimeUnit in spite of integer magic numbers
Calls to System#currentTimeMillis() changed to System#nanoTime().
Removed argument from SplashActivity#setMinDisplayTime()
Removed needless finally blocks
Introduced synchronized methods for accessing a backgroud thread state information.
Logged messages should now be more clear.
If parsing data XML fails application displays an AlertDialog and then is silently closed (NPE no more). Added a few strings (pl, en) for that dialog.
Opening SightseeingActivity after SplashActivity.
Added TODO notes (UT can be implemented for SplashActivity).
Merge remote-tracking branch 'upstream/android' into android

Conflicts:
	AndroidManifest.xml
	res/values/strings.xml