help documents, search dialog, save CWD, show data point info

• Documentation under menu Help: to view and search help documents #9 (closed)
• Display message dialogs for processing log and channels under different tabs with searching feature and interaction with channel plots. #4 (closed)
• Working directory are saved in DB and recalled when SOHView is opened. #8 (closed)
• Shortcut for Documentation and Main Data Directory
• Showing info of a clickable plotting data point #12 (closed)