- Correct the name to the apk to match the one generated.
- Fix typo on click on, and match the format on the rest of the
instructions instead.

The building from source instructions were written around the time
Android Studio (AS) was version 1.5. Since then, some prompts/options have
been removed or moved around. Thus, users willing to build from source
may get confused with the current instructions. Update the screenshots
to show a more version of AS (3.5), and remove the steps that are not
longer necessary.

* Rename shortcode hidingemail.html to contact.html
* Change content/ pages to new contact shortcodes