Include Soft Credits in contribution search

Allow user to include soft credit contributions from Find Contributions and Contributions panel in Advanced Search.

1. Add radio button filter in row below Payment Method:
Contributions OR Soft Credits? [ x ] Contributions Only [ ] Soft Credits Only [ ] Both

• "Contributions Only is default." (matches existing behavior)
• Query results include rows for either or both civicrm_contribution and civicrm_contribution_soft records meeting the search criteria
• Preferably contribution and contribution_soft rows follow requested ORDER BY as a UNION (i.e. if by received_date, all rows are ordered that way).

2. Add Drop-down: "Soft Credit Type" - which is displayed in same row to the right of the radio button above. Field should be hidden if "Contributions Only" is selected.

3. When soft credits are included in Find Contributions search results (or Advanced Search => Display Results as Contributions), add 3 columns to search results:

• Soft Credit For: contains sort_name of contact linked to the contribution that the soft-credit is associated (sort_name hyperlinks to contact/view for that contact)
• Soft Credit Amount (civicrm_contribution_soft.amount)
• Soft Credit Type

(These columns are blank for contribution rows and populated for soft-credit rows.)

3. Export

• Primary fields export should include the new columns above
• For contribution_soft rows we should also provide the associated contribution_id in separate column (Soft Credit For Contribution ID = civicrm_contribution_soft.contribution_id)
• Select fields for export should allow user to select the 4 columns above