WebUI: Simplify mission view control

[tbkoay]

When "toggle mission point" is off, the user may get confused by couldn't see the planned mission.

Suggest one of the followings (descending preference)

• [x] Mission > View button will toggle mission on-off. This may also solve #7
• [x] Automatically toggle mission view on when the mission
• [x] Provide status highlight of the toggle buttons.

Priority: LOW