scratch
test add parent and child action
test selection on the tree view
finish double click action, but not finish add node action yet
add drag listener
use setInput/getInput to change tree content
delete node addChild in content provider class
finish dynamiclly add leaf
use user input to create folder
1. can add folder and leaf at any selection
2. add project name info to TreeObject
1. add delete feature
2. add confirm dialog before detele
add gson to dump object to string and vise verce
move third-party lib to libs folder
finish persistent
do clean job
delete unused import
add double click to expand or collapse folder
1. add bookmark from selection on package explorer
delete unused import
add button to toolbar