performance optimizations: more index queues and improved database code

Merge pull request #145 from spacemansteve/PR145conflicts

uses priority queueing when updating prod, adds database and checksum optimizations

pin httplib2 to an older version

for python2 compatibility

pin httplib2 for python2 compatibility

it looks like that latest release of htttplib2 accidentally broke python2.

Include rebuild solr index tweak

v1.5.10

another quick fix: tweak solr parameter in index rebuild

Maintenance release

8428811 - Fix: delete all solr documents again via simple request

Maintenance release

#153 - Bugfix: new key for docsPending (used in reindex script)

Maintenance release

#147 - Allow sending records to alternate collections (e.g. collection2)
#149 - Bugfix: make rebuild script read the config file properly

Fixed index rebuild script

#146 - Collection rebuild was failing because of a faulty logging statement

adds options reindex_failed, disable updating timestamps and improved db error handling

Merge pull request #143 from spacemansteve/master

force message retry on update db error

resolve duplicate bibcodes in records table

code is in scripts directory