implement import front end #15
Description
Once the import back end is complete, implement front end to allow user to perform imports through web interface.
Import should be accessed from the Contributions and Expenditures index page for a given report.
The import option should be provided only if there are no records of the indicated type associated with the report.
Import workflow should be:
- user selects CSV for upload and submits
- file is loaded, each record is checked with model validations
- result is shown - how many records were seen, validated, failed
- user is asked whether to proceed with the import, with a warning that invalid rows will be ignored
- if the user says yes, than database records are added for all the valid rows