Implement Import UPDATE for Contributions and Memberships

Currently, Contribution and Member import only support "create" mode. We have implemented UPDATE ("On Duplicate Entries") handling for Participant in event/import. We should also support UPDATE functionality for the other two component imports.

Participant import matches to existing participant record on (Event Title + Contact Match) OR (Event ID + Contact Match). For contributions, safely match to existing records based on :

• Contribution ID (civicrm_contribution.id) OR Transaction ID (civicrm_contribution.trxn_id) OR Invoice ID (civicrm_contribution.trxn_id)
  and membership, based on primary key for now
• Membership ID (civicrm_membership.id)

Details:

• add "On Duplicate Entries" radio button to step 1

• IF onDuplicate = Update, then include an additional mapping option value (mapper selects)
  ++ for contribution -> "Contribution ID OR Transaction ID OR Invoice ID (update existing contribution)"
  ++ for membership -> "Membership ID (update existing membership)"

• modify import processing to handle find >> update

• if onDuplicate = Update, and a Contribution/Membership ID is NOT NULL for a row, we must find a matching record. If we don't - then skip the row and add to error array / error file download. Error msg = "Matching Contribution record not found for Contribution ID 5233. Row was skipped." (same error msg for Membership, just change record type)

• include count of new AND updated records in import summary