Use StringBuilder for intermediate output in CreateHtml5FromXml
Use StringBuilder for intermediate output in CreateHtml5FromXml

Avoids writing twice in rapid succession to the same temp file, which may be the cause of BL-94.

andrew-polk/BloomDesktop,JohnThomson/BloomDesktop,StephenMcConnel/BloomDesktop,StephenMcConnel/BloomDesktop,andrew-polk/BloomDesktop,JohnThomson/BloomDesktop,BloomBooks/BloomDesktop,gmartin7/myBloomFork,StephenMcConnel/BloomDesktop,BloomBooks/BloomDesktop,StephenMcConnel/BloomDesktop,JohnThomson/BloomDesktop,StephenMcConnel/BloomDesktop,JohnThomson/BloomDesktop,gmartin7/myBloomFork,BloomBooks/BloomDesktop,gmartin7/myBloomFork,gmartin7/myBloomFork,JohnThomson/BloomDesktop,gmartin7/myBloomFork,BloomBooks/BloomDesktop,BloomBooks/BloomDesktop,BloomBooks/BloomDesktop,andrew-polk/BloomDesktop,StephenMcConnel/BloomDesktop,andrew-polk/BloomDesktop,andrew-polk/BloomDesktop,gmartin7/myBloomFork,andrew-polk/BloomDesktop