#18 Site settings: added new tabs; fixed rendering of dates;
#18 Changed formatting of returning saved page dates
#18 Image selection logics in edit blog form
#18 Refactored pages table: added reference to Image, removed ImageUrl
Module descriptors registration: concurent dictionaries changed to dictionaries
Merge remote-tracking branch 'remotes/origin/dev' into dev-blogs
#18 Fixed rendering of blog post image