QuotaAwareStore support from IMAP provider

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12. Add PreencodedMimeBodyPart class (6301386)
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In some cases an application will have data that has already
been encoded using (for example) base64 encoding.  There should
be an easy way to attach such data to a message without the need
to decode it and reencode it.  This class provides such support.

/**
 * A MimeBodyPart that handles data that has already been encoded.
 * This class is useful when constructing a message and attaching
 * data that has already been encoded (for example, using base64
 * encoding).  The data may have been encoded by the application,
 * or may have been stored in a file or database in encoded form.
 * The encoding is supplied when this object is created.  The data
 * is attached to this object in the usual fashion, by using the
 * <code>setText</code>, <code>setContent</code>, or
 * <code>setDataHandler</code> methods.
 *
 * @since       JavaMail 1.4
 */

public class PreencodedMimeBodyPart {
    /**
     * Create a PreencodedMimeBodyPart that assumes the data is
     * encoded using the specified encoding.  The encoding must
     * be a MIME supported Content-Transfer-Encoding.
     */
    public PreencodedMimeBodyPart(String encoding)
}