Sets the read-only mode of the component to the specified mode. The user
can not change the value of a read-only component.
As only
AbstractField or
LegacyField components normally
have a value that can be input or changed by the user, this is mostly
relevant only to field components, though not restricted to them.
Notice that the read-only mode only affects whether the user can change
the value of the component; it is possible to, for example, scroll
a read-only table.
In Vaadin 8 the read-only property is part of
HasValue API.