Add ProjectOpenedHook

- Ask whether you want to run halt command when project will be closed if status is running
Add settings to project properties

- none : do nothing
- halt : run halt command
- halt-ask : popup a question dialog
Update README
Move message
Merge pull request #20 from junichi11/project-opened-hook

Add ProjectOpenedHook
Update version number to 0.5.0
Merge branch 'dev'