SplitLayout documentation has no explanation of MasterContent and DetailContent classes

[javier-godoy]

The SplitLayout example references MasterContent and DetailContent classes, but it doesn't explain that they are components.

docs/src/main/java/com/vaadin/demo/component/splitlayout/SplitLayoutBasic.java

Lines 13 to 14 in f5fa017

	MasterContent master = new MasterContent();
	DetailContent detail = new DetailContent();

[rolfsmeds]

Actually, instead of explaining badly chosen classnames, we could just rename those example components to something like FirstComponent and SecondComponent – would that make it obvious enough that these are examples?