f# model with some failing tests
Commit .suo prior to removing it.
F# library parallels functionality of the C# library.
Revised for better layout.
Additional properties for PeriodItem and Period.
Wiring up properties in PeriodItem
Additional tests for PeriodItem
Revision of calculations and completion of ClosingStock related properties.
Start migrating tests to f#/fsunit
Finished moving Period tests to fs, now moving SalesItem tests.
Moved SalesItem tests to FsUnit.
Moving PeriodItem tests to FsUnit.
Building up PeriodItem tests in FsUnit.
All tests moved to FsUnit; c# test project removed from the solution.
Merge branch 'FSharp'

Conflicts:
	StockCheck.v11.suo
Removal of c# model; renaming of projects and folders.
Added ValueOfQuantity function to simplify PeriodItem properties.