(#2143) Get PouchDB's scripts to run properly on Windows

Attempt to resolve #2143 

bin/build-plugin.sh - Fixed the path to work on Windows and deleted the
 duplicate line.

package.json - For calls to sh scripts change the call from being a path
 starting with './bin/' to start with 'sh bin/' and change calls to js
 files to change from './bin/' to 'node ./bin/'. Also had to set
 run-test.sh to use 'bash' and not 'sh' because it's a bash script.

test.attachments.js - Remove checks for digest values. They are absolutely
 not intended to be repeatable so checking them is not semantically valid.
 And the ones generated by CouchDB on Linux and Windows differ (as is
 explicitly allowed by the CouchDB definition)