[#103] Update address field to be consistenly editable.

Technical:

- No longer use placeholder
- Only use input value

Usability:

- input value is always displayed in the same style
- input value is always editable
- entering a blank input value will reset to value before the edit

Tested:

- iPhone 5 iOS7
- Nokia 920 WP8
- Android Galaxy Nexus 4.3