changed all 'class' to 'data-status' for values of 'draft' and 'informal'
added 'data-status' attribute and Wiki page
updated 'data-status' styles
minor changes to 'data-status' css
rearranged some css files
Merge branch 'develop' into feat#6-status

Conflicts:
	core/styles/all.css
	core/styles/typo/text/_doctext.less
Merge branch 'develop' into feat#6-status

Conflicts:
	core/styles/all.css
updated classical music blog post
updated headings blog post; deleted dog-training blog post
fixed data-status on HTML blog posts

TODO: convert TODO items (from `/blog/TODO.md`) to GitHub issues

closes #6
Merge branch 'feat#6-status' into develop