Added long-press popup menu to WebView in SingleMessageView

Actions:
- Open link for viewing
- Share link
- Copy link to clipboard
- View image
- Download/save image
- Copy image URL to clipboard
- Call number
- Save phone number to Contacts
- Copy phone number to clipboard
- Send mail
- Save to Contacts
- Copy email address to clipboard

This is based on work done by kernelhunter92 and ShellZero.

Fixed issue 1248