barChart/edit - Edits an existing bar chart.

Method parameters:
id - The ID of the bar chart to edit.
name - The new name of the bar chart.
tags - A space-separated list of tags.

Returns a JSON document of the following format:
<boolean> - Always true.

Expected errors:
BAR_CHART_NOT_FOUND - A bar chart with the ID doesn't exist.
ENTER_NAME - The new name is empty.
TOO_MANY_TAGS - More than 5 tags given.