Enable Screenshots setting

Also, moved activity restart functionality to LockableActivity (needed
for recreating the whole activity when switching language or toggling
the enable screenshots setting)
Merge branch 'master' into master_feature_3247

Conflicts:
	app/src/info/guardianproject/securereaderinterface/LockableActivity.java
Use mPrefs from super class
Use latest library
Merge branch 'master' into master_feature_3247
Merge pull request #73 from N-Pex/master_feature_3247

Master feature 3247