Merge pull request #13 from liuzhaoguo/master

add region grow function
Refactor code
fix bug in main.py
fix bugs while refactoring, and fix a OS X bug in main.py
modify some settings
fix bug in time point selection
Merge pull request #14 from sealhuang/fix-gui-action

Refactor the structure, including add 4D data support, reduce complex signal connection, etc.
fix time selection bug in main.py
remove Unified ToolBar in Mac
Merge pull request #15 from sealhuang/fix-time-point-selection-bug

Fix time point selection bug
fix time selection bug
Merge pull request #16 from sealhuang/fix-time-selection

fix time selection bug
Fixed 'cross_display' bugs,users can determine whether to display the mouse crosshairs by chosing the corresponding item under the toolbar.
Fixed 'cross_display' bugs.The users can decide whether to display the mouse cross by chosing the corresponding item in the toolbar
Merge pull request #18 from zhouguangfu/master

display the cross hover or not
Using 'set_cross_status" function to define the status of the mouse hover.
Using "set_cross_status" function to define the status of the mouse hover.
Merge pull request #19 from zhouguangfu/master

Fix mouse hover status
update TODO
Merge pull request #20 from sealhuang/update-todo-list

update TODO