Social Share

This PR is for preview! Please do not merge this...
- Testing the basic functions.
- Uses $context['canonical_url']
- Uses static share URLs
- No JS/Ajax used (both sided no FB/Twitter/G+ JS files included too)
- Has only enable-disable function (requested by Oldiesmann)
- Includes: Facebook - Google+ - Twitter only.

Signed-off-by: Antes <antes@simplemachines.org>