Enable loan stats only if "loanstats" feature is enabled in the config.
Fixed unicode error in solrwriter.
Implemented support for arbitrary time periods in lending stats.

The start and end dates can be specified as query parameter.
/stats/lending?t=20131001-20131201
Fixed issue in displaying loan stats for longer duration.

By default, solr limits the number of facets displayed to 100. That was
causing lot of dates to disappear, causing broken graph.

Fixed it by setting facet.count to very large value.
Added ability to load specified entries and all entries from a last update to process_stats.py.