Provide source context with error

[nikku]

With these changes we provide proper context for errors:

ERROR in ./src/header.html
Unexpected token (14:23)
12:     },
13:     computed:
14:       salutation(dude) {
                           ^
15:         return hello(dude);
16:       }
 @ ./src/counter.html 3:0-30
 @ ./src/index.js
 @ multi index

Before errors were shown with their message only and excluded the frame data.