Improve layout of calendars and schedule lists in sample themes

[doersino]

Calendars and schedule lists are difficult to adapt to slides:

• Given a schedule list in Markdeep source code, Markdeep generates a calendar and, below that, a schedule list.
• There's no way both of them would fit on a single slide for even moderately busy schedules.
• They're both tables, with some lengths defined inline in terms of pixels – these need conversion to rem.

I likely won't tackle this anytime soon since I've yet to use a schedule list myself, but it's certainly worth taking at stab at.