Rename "push quickstart" repos

the following repos have bad names:

• aerogear-push-quickstart-backend
• aerogear-push-quickstart-web
• aerogear-push-quickstart-ios
• aerogear-push-quickstart-android

The AeroDoc is more a 'topic demo' (see old ML thread) and it's really not a 'quickstart' (due to complex setup).

Hence the repo names are confusing. Proposal: Let's rename the GH repos:

• aerogear-aerodoc-backend
• aerogear-aerodoc-web
• aerogear-aerodoc-ios
• aerogear-aerodoc-android