Histograms rewrite

[retabak]

• misconceptions json
• objectives json
• Rewrite will remove comparison to bar charts (now unneeded + more effective later)
• Rewrite will include instruction on histogram center/ spread / variability
• Rewrite will include more basic interpretation questions
• Add histogram activities from Joy #2226
• further scaffold matching box plots and histos #2198
• add section or worksheet on "variability" to "visualizing the shape of the data"  #2085
• histograms - address the question of whether the values representing a single bin's boundaries (min and max) are part of the lower bin or the higher bin
• discuss shape during histograms lesson #2177