Added support for HasMediaLibrary when Flexible is used in Nova-Page

Fixed ScopedRequest::isFlexibleStructure method. Closes whitecube#56

Fixed multiple nested flexible fields registration

Removed unnecessary use statement

Guard against non-existant request attribute - Closes whitecube#38

Merge branch 'master' of github.com:whitecube/nova-flexible-content

Fixed nested flexible fields in Nova 2.0.3

Updated Resolver code formatting. Closes whitecube#9

Merge branch 'master' of https://github.com/whitecube/nova-flexible-c…

…ontent

Fixed group values persistance after group key change