STS output warnings

The current STS generation leads to multiple warnings.

@Intelligent2013 can you help check? Thanks!

```
Validate XML againts XSD NISO-STS-extended-1-MathML3-XSD/NISO-STS-extended-1-mathml3.xsd...
/Users/me/src/glossarist/iev-document/site/documents/iec-60050-192.sts.xml is NOT valid reason:
[ERROR] org.xml.sax.SAXParseException; systemId: file:/Users/me/src/glossarist/iev-document/site/documents/iec-60050-192.sts.xml; lineNumber: 484; columnNumber: 20; cvc-complex-type.2.4.a: Invalid content was found starting with element 'verbal-definition'. One of '{disp-formula, disp-formula-group, chem-struct, inline-formula, "http://www.w3.org/1998/Math/MathML":math, bold, fixed-case, italic, monospace, num, overline, roman, sans-serif, sc, strike, underline, ruby, sub, sup, def-list, list, fn, target, xref, citation-alternatives, element-citation, mixed-citation, std, break, named-content, styled-content, address, alternatives, array, boxed-text, chem-struct-wrap, code, fig, fig-group, graphic, media, non-normative-note, normative-note, non-normative-example, normative-example, notes-group, preformat, supplementary-material, table-wrap, table-wrap-group, email, ext-link, uri, inline-graphic, private-char, "urn:iso:std:iso:30042:ed-1":entailedTerm}' is expected.
[ERROR] org.xml.sax.SAXParseException; systemId: file:/Users/me/src/glossarist/iev-document/site/documents/iec-60050-192.sts.xml; lineNumber: 510; columnNumber: 20; cvc-complex-type.2.4.a: Invalid content was found starting with element 'verbal-definition'. One of '{disp-formula, disp-formula-group, chem-struct, inline-formula, "http://www.w3.org/1998/Math/MathML":math, bold, fixed-case, italic, monospace, num, overline, roman, sans-serif, sc, strike, underline, ruby, sub, sup, def-list, list, fn, target, xref, citation-alternatives, element-citation, mixed-citation, std, break, named-content, styled-content, address, alternatives, array, boxed-text, chem-struct-wrap, code, fig, fig-group, graphic, media, non-normative-note, normative-note, non-normative-example, normative-example, notes-group, preformat, supplementary-material, table-wrap, table-wrap-group, email, ext-link, uri, inline-graphic, private-char, "urn:iso:std:iso:30042:ed-1":entailedTerm}' is expected.
[ERROR] org.xml.sax.SAXParseException; systemId: file:/Users/me/src/glossarist/iev-document/site/documents/iec-60050-192.sts.xml; lineNumber: 528; columnNumber: 20; cvc-complex-type.2.4.a: Invalid content was found starting with element 'verbal-definition'. One of '{disp-formula, disp-formula-group, chem-struct, inline-formula, "http://www.w3.org/1998/Math/MathML":math, bold, fixed-case, italic, monospace, num, overline, roman, sans-serif, sc, strike, underline, ruby, sub, sup, def-list, list, fn, target, xref, citation-alternatives, element-citation, mixed-citation, std, break, named-content, styled-content, address, alternatives, array, boxed-text, chem-struct-wrap, code, fig, fig-group, graphic, media, non-normative-note, normative-note, non-normative-example, normative-example, notes-group, preformat, supplementary-material, table-wrap, table-wrap-group, email, ext-link, uri, inline-graphic, private-char, "urn:iso:std:iso:30042:ed-1":entailedTerm}' is expected.
[ERROR] org.xml.sax.SAXParseException; systemId: file:/Users/me/src/glossarist/iev-document/site/documents/iec-60050-192.sts.xml; lineNumber: 554; columnNumber: 20; cvc-complex-type.2.4.a: Invalid content was found starting with element 'verbal-definition'. One of '{disp-formula, disp-formula-group, chem-struct, inline-formula, "http://www.w3.org/1998/Math/MathML":math, bold, fixed-case, italic, monospace, num, overline, roman, sans-serif, sc, strike, underline, ruby, sub, sup, def-list, list, fn, target, xref, citation-alternatives, element-citation, mixed-citation, std, break, named-content, styled-content, address, alternatives, array, boxed-text, chem-struct-wrap, code, fig, fig-group, graphic, media, non-normative-note, normative-note, non-normative-example, normative-example, notes-group, preformat, supplementary-material, table-wrap, table-wrap-group, email, ext-link, uri, inline-graphic, private-char, "urn:iso:std:iso:30042:ed-1":entailedTerm}' is expected.
```