User experience improvements:

• Add welcome activity with a short introduction
• Add version info and GitHub link to info activity
• Do not require two long clicks for first time start
• Warn user about missing configured hosts files
• Improve various user-facing strings

Bugfixes:

• Fix downloading of hosts files on Lollipop
• Support host files containing only one column
• Correctly lower-case host names for comparisons

Legal:

• Include copyright, COPYING, and LICENSE.Apache-2.0 in the generated APK