Example: Rename Text example to TextEditor

Text is too generic.

Change-Id: I68d304345d2982a8acc8843c4c843e9f5e696954
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>