Remaining Plateau issues with reverse_adoc

[ronaldtse]

The remaining issues are at:

• reverse_adoc: merge exe/reverse_adoc into coradoc CLI #64
• reverse_adoc: Full-width spaces should be trimmed on titles #65
• reverse_adoc: Numbering in clauses should be removed #66
• reverse_adoc: Paragraphs should not retain flanking full-width spaces #67
• reverse_adoc: List item depth is dependent on context #68
• reverse_adoc: Clause levels 4 and 5 for Plateau document #69
• reverse_adoc: If image has no options, don't write any #70

Originally posted by @ronaldtse in #61 (comment)