DEMO APP NEW FEATURE: added large video example share option
NEW FEATURE: SHKDropbox can get user info
NEW FEATURE: SHKDropbox user can select target folder
REFACTORING: Overwrite file check - instead of complicated custom dropboxForm user gets alert asking if he wants to overwrite file on Dropbox. The form opens only if dropboxShouldOverwriteExistedFile is YES in configurator and the file actually exists on Dropbox (it has not been deleted, thus does not exist in revisions only)
BUGFIX: if unauthenticated user shares on Dropbox, share form is shown after successful authentication.
BUGFIX: fixed SHKDropbox revoked access behaviour to conform with ShareKit
DEMO APP: added additional Dropbox api key for sandbox permissions
REFACTORING: SHKDropbox implementation simplified
CLEANUP: SHKDropbox removed obsolete strings
Merge branch 'master' into DropboxRewriteOptions

* master:
  BUGFIX: fixes #848 - SHKiOS sharers now handle authorisation result more transparently.
  BUGFIX: localization typo, fixes #844
Merge branch 'master' into DropboxRewriteOptions

* master:
  BUGFIX: fixed bad logic which preferred SHKFacebook instead of SHKiOSFacebook
  BUGFIX: SHKTwitter now automatically shows login UI after detecting invalid token. Fixes #838
REFACTORING: minor SHKDropbox cleanup, updated comments etc
BUGFIX: SHKDropbox fixed memory leak
NEW FEATURE: successful share service’s response is included in SHKSendDidFinishNotification’s userInfo. Implemented by Dropbox only at the moment. This ShareKit wide solution replaces proprietary kSHKDropboxSharableLink notification, which becomes deprecated.
BUGFIX: SHKDropbox uses kSHKDropboxDestinationDir value, if pre filled
REFACTORING: added Dropbox specific sharer extension to SHKItem (dropboxDestinationDirectory). Deprecated kSHKDropboxDestinationDir custom value. SHKItem’s customValues should never be used outside sharer’s implementation. Otherwise the possibility to use them is buried within implementation - users are not aware that they can use it. Sharer specific extensions are much more user friendly and transparent.