make EventResult.result_value behave like Result.value
allow Report.entered to be overridden
allow blank (but not null) to make form submission work
allow empty string in nested key
use fewer queries when updating a large number of EventResults
use bulk_create when updating a large number of EventResults
support arbitrary Event natural keys
don't look up dbio UnknownItems when resolving url slugs
name columns to avoid 'None' in pandas utf-8 csv output
ignore columns other than 'value' when computing boxplots; include count in output
additional EventResult optimizations
add Scatter plot and a few docstrings
utilize LocalDateTimeField
result_value should be property
handle empty indexes with rest_pandas
update ContentType cache usage
Merge pull request #19 from wq/vera2

more vera improvements