Improve doc of types
Doxyfile tweaks: fix casing and enable STL support
Style tweaks for <code>
Doc the log levels
Fix `i.e.`s that break brief docs
Style tweaks for <em>
Travis trigger
Merge pull request #102 from utensil/80-engine-api-doc

Improve `engine` API doc: Types and misc
Merge remote-tracking branch 'upstream/master'

Conflicts:
	Doxyfile