Trying HTML build with 2.0.15

Olinks fail to be resolved in this commit.
Partial fix for DOCS-133

Get olinks working in chunked HTML
Additional fix for DOCS-133

Resolve olinks in single-page HTML
Fix for DOCS-134

The inter-PDF links don’t quite actually work, but this seems no worse
than what we have now.
Fix for DOCS-135
Hack^^^^Fix for DOCS-136

This uses 2.0.14, but only for RTF
Merge pull request #8 from markcraig/DOCS-81

Fix for DOCS-81: Evaluate impact of a move to docbkx-tools 2.0.15