[doc] Replace info icon
[doc] Replace info icon

Use a monochrome icon for additional info.
Taken from MIT licensed ionic icon set: http://ionicons.com/

Change-Id: I07867b5e48b7138bd9ab30c842a3000cee3e2084

eclipsesource/tabris-js,eclipsesource/tabris-js,eclipsesource/tabris-js