Created skeleton 'IntroActivity'

The activity will be used to display the app logo and to get some basic
user information, like the users location and maybe the occasion of the
visit(education, sports).
Added ViewPager navigation to the Intro activity
Added activity declaration to the manifest

Also changed the minimum and target SDKs.
Removed the dummy layout fragment and created a simple welcome fragment

Created a simple layout for the fragment that'll be show to the user the
first time he visits the app, before he chooses his location of
exchange.
Made PagerTitleStrip 'gone'

Removed the PagerTitleStrip from the layout. Maybe alter it'll be of
use.
Created three separate fragments for the three intro steps

Updated the intro activity to display the three, for now, dummy
fragments that'll be used to get the users location or destination.