Add MultiSelect. Separate Selection into different file. Press Shift and click to multi select
Allow Drag of all selected nodes. Bug fixed for add selection
Separate keyboard and mouse commands into separate file.
Refactor Selection functions
Add Drag Select functions.
Disable drag select for panning. Bug fixed for drag select
Refine axis boundary settings to fix bugs in drag selection
Refine seletion mechanism and selection highlight color
Reorganize nodes and links data objects with Javascript prototype
Add underscore library
Merge remote-tracking branch 'origin/selection-test'