Minor refactoring

Removed some code duplication
rename embed > embedded to signal that it's a state and not an action
Use more explicit name
inlined method used only once
Formatting
display more slides in overview
fix bug that caused slideshow to break if an unexisting named link was used
a few corrections to overview slide positioning
correction to view distance calculation for vertical slides
disable transitions while presentation loads
move leap styles to js #554
merge dom setup refactor #544