Refactore page installer and extend schema format

Api/ContentEntryInstallerInterface.php

Api/ContentInstallerInterface.php

Api/Data/PageEntryInterface.php

Model/Command/ApplyPageEntry.php

Model/Config/Converter.php

Model/Config/Converter/AttributeValueParser.php

Model/Config/Converter/BlockNodesParser.php

Model/Config/Converter/ChildNodeValueParser.php

Model/Config/Converter/ContentElementKeyBuilder.php

Model/Config/Converter/ContentHeadingParser.php

Model/Config/Converter/ContentNodeParser.php

Model/Config/Converter/CustomDesignNodeParser.php

Model/Config/Converter/DesignNodeParser.php

Model/Config/Converter/PageNodesParser.php

Model/Config/Converter/SeoNodeParser.php

Model/Config/Converter/StoresNodeParser.php

Model/Config/Converter/TitleNodeParser.php

Model/Console/PagesListCommand.php

Model/ContentEntry.php

Model/ContentInstaller.php