[libsocialcache] Use Qt4 signal connection syntax for image replies

This commit changes the connection from the Qt5 syntax back to the
dynamic Qt4 syntax, as the Qt4 syntax fixes an issue whereby oopp
sync plugins couldn't download avatar images.
Merge pull request #48 from chriadam/fixnetwork

[libsocialcache] Use Qt4 signal connection syntax for image replies
Bump version
[libsocialcache] Initial VK database support
[libsocialcache] Improve VKNotificationsDatabase API
[libsocialcache] Added QML model for VK posts
[libsocialcache] Use string instead of int for 'Type' value in VK notifications database