Merge pull request #88 from oerpub/58426912-58572696-use-element-name

use actual label instead of literal "this element"
remove boxy styling from definitions

style it more like an exercise / as in mock-up / as in cnx
make "copy element" option less conspicuous
improve styling of x and gear

make them lighter since i apparently can't make them thinner :-(
better spacing (centered and without extra space above/below)
hover behavior more like mock-up
update styling of quotations

use left/right quote mark images instead of generic box to style
quotations
remove "extra" padding around figures
transition height for solution-controls too ...

... so that exercises don't take up as much space when not hovered
style multiparts like other exercises

i.e. without the boxiness
hide "click to add part" on mouseleave

space-saving measure same as it's done for regular exercises
make blue droppable area less tall

plus a little margin so it doesn't look too awkwardly close to the
elements it'll be between.
remove excessive and redundant min-heights
Merge remote-tracking branch 'origin/58657378-boxes-and-spacing-2nd-attempt' into testing

Conflicts:
	src/plugins/oer/definition/css/definition-plugin.css