Use label for generating id

[ripla]

When connecting an element to Java,
I want to see meaningful names for the java fields,
so that I can better use the fields in my Java app

Use label attribute to try and generate a better field name when connecting to Java. The used attribute must contain a valid Java field name.

Scenarios

Label used for Java field name when Id is not set

Given a new Flow template with a "vaadin-button"
And the vaadin-button "id" attribute value is empty
And the vaadin-button "label" attribute value is "barfoo"
When the user connects the "vaadin-button" to Java
Then the Java companion file contains "private Button barfoo"
And the vaadin-button "id" attribute value is "barfoo"