Add social Sharing plugin

Requires more work for making it work with all platforms

// NOTE: shareViaSms -> access multiple numbers in a string like: '0612345678,0687654321'
// NOTE: shareViaEmail -> if user cancels sharing email, success is still called
// NOTE: shareViaEmail -> TO, CC, BCC must be an array, Files can be either null, string or array
// TODO: add support for iPad
// TODO: add support for Windows Phone
// TODO: detailed docs for each social sharing types (each social platform has different requirements)