Consolidated Schema uses bibl/ref to point to manuscripts, we use bibl/ptr, we should probably normalize to their method?

Thoughts? This would introduce use of ref for both works and manuscripts but we could control by @type

<div xml:id="refsToMSS">
                        <head>References to other manuscripts</head>
                        <p>References in the description to other manuscripts should be enclosed in
                                <gi>bibl</gi> tags with <att>type</att> of value <val>MS</val>. The
                                <att>subtype</att> may be used to indicate if the manuscript is held
                            by the same institution that holds the manuscript being catalogued
                            (value <val>interal</val>) or by another institution (value
                                <val>external)</val>. In the former case, the shelfmark should not
                            include the location or institution name; in the latter case, location
                            and institution should be included.</p>
                        <p> The <gi>ref</gi> element may be used to provide a link to an online
                            catalogue or digital fascimile. <egXML
                                xmlns="http://www.tei-c.org/ns/Examples"> Eberbach, Cistercian abbey
                                (?): ‘modern’ chapter numbers added in boxes in the margin, as in
                                    <bibl type="MS" subtype="internal">MS. Laud Lat. 107</bibl>. </egXML>
                            <egXML xmlns="http://www.tei-c.org/ns/Examples"> This scribe was also
                                responsible for most of the Simeon manuscript (<bibl type="MS"
                                    subtype="external"><ref
                                        target="http://www.bl.uk/manuscripts/FullDisplay.aspx?ref=Add_MS_22283"
                                        >London, British Library, Add. MS. 22283</ref></bibl>) but
                                has not yet been identified in any other manuscripts or documents.
                            </egXML>
                        </p>
                    </div>

srophe / britishLibrary-data

Consolidated Schema uses bibl/ref to point to manuscripts, we use bibl/ptr, we should probably normalize to their method? #1553