Kivyblocks

* add Behavior handle when build Widget by blocks
* support following behaviors
1 ButtonBehavior
2 CodeNavigationBehavior
3 CompoundSelectionBehavior
4 CoverBehavior
5 DragBehavior
6 EmacsBehavior
7 FocusBehavior
8 ToggleButtonBehavior
9 TouchRippleBehavior
10 TouchRippleButtonBehavior
11 BGColorBehavior
12 ModalBehavior
13 swipeBehavior
14 videoBehavior
* DataGrid class add checkbox support

* uses weakref to collect all the i18n widgets in i18n.py
* show video play position

add script to support local .tmpl and .dspy file translation. it can build dynamic user interface without remote server.