Baseline alignment of widgets about tabris-js

[ralfstx]

Part of #66

[ralfstx]

We agreed on adding a new property baseline to layoutData that currently only accepts the reference to another widget.

In the future, we may also support [widget, offset].

At the moment, this property is only supported for widgets that contain text, i.e. both the actual and the referenced widgets must be one of Label, Button, or Text.

For multiline texts, the platforms differ: Android aligns on the first line, iOS on the last line. On both platforms, this behavior doesn't seem to be changeable, so we have to live with this difference for now.

[mpost]

We should have created a mission statement bug at #1 which should have been open forever. :)