Excluded case of trying to determine mime type for empty string.

Refactored downloader for local files.

Items duplication adapted to new ideology of adding media items on the board.

Have a problem - should take care about saving original src path.

Document navigator: "Add pages from file" isn't work with old UBZ

Show Desktop: "Erase all" button isn't work

Changing the languages of the virtual keyboard crashes the software

Changing the languages of the virtual keyboard crashes the software

Corrected adding items to group.
Corrected group creation.
Corrected adding items to scene - items shouldn't be added to itemsToRemove list because that list needs for cleaning undo stack.
Improved mechanism of removing "itemsToRemove".
Removed wrong deletion of mButtons list from UBGraphicsItemDelegate destructor because that buttons has Frame as parent.
Removed possible memory leak in UBBoardController::clearUndoStack. Some items was able not deleted.
tmpScene in cffReader not deletes now because ithas a proxy as parent.

Improvement of scene update flag setting

Trying to position ToolWidget at the right place to move naturally from widgetitem to toolidget.

Fix is obvious but it probably hides something.

Implemented Sankore-729 - previews images for web search results supports images, audios, videos and flash content.
Images previews is adjusted now.
Mime type detection mechanism is more common now.