code refactoring
- separate the model, view code
add sample document
Merge pull request #518 from jeongjaehong/1.4.1

Alter table Dialog.
chart bar size is 250.
fixed called widget
fixed column null is show empty.
fixed package name.
com.hamgum.tadpole.help.code to com.hangum.tadpole.help.core
enhancement 

https://github.com/hangum/TadpoleForDBTools/issues/520
fixed url redirect error:
https://github.com/hangum/TadpoleForDBTools/issues/521
지원되지 않는 브라우저가 있을경우 에러메시지가 나올수록 수정했습니다.
Merge pull request #6 from hangum/1.4.1

1.4.1