[sailfish-browser] First use with real tabs. Contributes to JB#17886
Merge pull request #75 from veskuh/refactor-start

[sailfish-browser] First use with real tabs. Contributes to JB#17886
Send available composition size to embedlite components when virtual keyboard open

Requires: https://github.com/tmeshkova/embedlite-components/pull/49
Decrease input field target size
Minor clenaup for DeclarativeWebPage

- parent is QQuickItem pointer
- container property is read-only to QML side