Add support for importing QIF files

[AArnott]

This isn't all done, mostly because the data model we're importing to doesn't represent everything that QIF can. We'll get more of that as we go.

Closes #99

[codecov-commenter]

Codecov Report

Merging #102 (72092f6) into main (8476f83) will increase coverage by 1.48%.
The diff coverage is 57.68%.

@@            Coverage Diff             @@
##             main     #102      +/-   ##
==========================================
+ Coverage   40.38%   41.87%   +1.48%     
==========================================
  Files          97      101       +4     
  Lines        7060     7788     +728     
==========================================
+ Hits         2851     3261     +410     
- Misses       4209     4527     +318     

Impacted Files	Coverage Δ
src/MoneyMan.WPF/UserNotification.cs	5.26% <0.00%> (ø)
...Management/ViewModels/InvestingAccountViewModel.cs	80.20% <0.00%> (-7.30%)	⬇️
...oneyManagement.Tests/Adapters/AdapterTestBase`1.cs	0.00% <0.00%> (ø)
....MoneyManagement.Tests/Adapters/OfxAdapterFacts.cs	0.00% <0.00%> (ø)
....MoneyManagement.Tests/Adapters/QifAdapterFacts.cs	0.00% <0.00%> (ø)
...bank.MoneyManagement.Tests/UserNotificationMock.cs	10.34% <ø> (ø)
...t.Tests/ViewModels/BankingAccountViewModelTests.cs	0.00% <0.00%> (ø)
...ent.Tests/ViewModels/MainPageViewModelBaseTests.cs	0.00% <0.00%> (ø)
...nk.MoneyManagement/ViewModels/DocumentViewModel.cs	69.85% <19.29%> (-12.13%)	⬇️
...rc/Nerdbank.MoneyManagement/Adapters/QifAdapter.cs	90.83% <90.83%> (ø)
... and 10 more

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