Add ApplicationReportGenerator header spec.

Add spec checking the default output for ApplicationReportGenerator, expecting just a header when given an empty list.
Add realistic ApplicationReportGenerator spec.

Add spec checking the output of ApplicationReportGenerator for a populated SubmissionRecordList.
WIP: Draft of ApplicationReport#to_string output.
Merge branch 'big_report' into big_report_merge
Fix variable mis-identification in spec.

Fix variable mis-identification (instance but meant local) for AggregateReportGenerator spec.
Apply Visitor pattern to ApplicationReport.

Refactor ApplicationReport to use Visitor pattern.

Refactor ApplicationReportGenerator to use ApplicationReport#display_on.

Refactor Application#display_on to avoid duplication.

Move #display_*_name methods from Name to Jobseeker and Recruiter, as names were getting duplicated.

Refactor SubmissionRecord to supply a String to #display_date instead of a Date, in keeping with the interface.
Update interactions.md with feature addition.