ReqMgr Oracle/CouchDB consistency work

Second round of Oracle -> CouchDB updates and checks.
ReqMgr CouchDB now consistent where it was achievable.
Dispensable CouchDB request fields not yet removed.
Prepared series of checks, as described in the README
    file, to be run later on again and should be very
    quick to perform.
README file updated with useful Oracle SQL queries checks.
All, table-by-table, steps comprehensively described on the
    #4388 ticket.

For attention: @ticoann
Merge pull request #4600 from zdenekmaxa/reqmgr-fixing-database-consistency-issue-4388-4

ReqMgr Oracle/CouchDB consistency work