WIP: Sailfish: Switch out SilicaWebview for SailfishWebview

[Thaodan]

This change replaces the WebKit based Webview witha Gecko based Webview. Busyindicator is not needed since SailishWebview provides its own.

WIP because:

• PulleyMenu doesn't work right now
• Navigation between the opened and the last opened page doesn't work