Re-instate package statistics for embargoes and sizes

The old code for package statistics was a quick hack that used OAI and
METS to calculate package-level embargo and size information. Removed
this old code and replaced it with proper calls to the DSpace data
model.

Also improved debugging output to indicate why items are being skipped
when the package statistics are generated.
Don't skip items with missing article DOIs

Many valid items will be in this state, because the curators have not
had a chance to add an article DOI yet.
Improve handling of Context object

Before, the Context was getting closed prematurely, so data file
information could not be queried.
Quote placeholder names

This allows them to be output correctly for use in a CSV
file. Technically, it shouldn't be necessary, but some spreadsheet
programs aren't very good at handling CSV.
Reinstate manuscript numbers in data package report
Update date handling for data package report
Make profileformats more palatable

Add commas to this report so it can be treated as a CSV file. Remove
the "Known/Unknown" indicators, which we rarely use in reports.
Count ReadMe files in each package
Add indication of whether a package has gone through journal review

This doesn't work well, because the provenance metadata doesn't
include the correct information. However, I want to keep this in the
report, so we have it when the provenance metadata is more correct.
Add reporting for whether a journal allows embargo and/or review
Remove extraneous comma in the output.
Merge pull request #240 from datadryad/trello-75

Updates to statistics reporting