doc/Doxyfile: bump to version 1.8.3.1.
ductpp.sublime-project: exclude `doc/html/` to prevent generated files from showing up in goto panel.
CharacterRange: renamed properties `start` and `end` to `first` and `last`.
ductpp.sublime-project: exclude all dirs from root and build data from test/.
Parser: made IO::StreamContext-taking ctor explicit, by-value & move.

NB: ScriptParser also updated.
ScriptWriter: made IO::StreamContext-taking ctor by-value & move.
Variable: corrected value types in value ctors.
doc/Doxyfile: put enum members on a single line.