Replace array types with `TArray<T>` specialisations

[delphidabbler]

TStringDynArray can be replaced with TArray<string> or array of string as appropriate.

Similarly TPJEnvironmentVarArray can be replaced by TArray<TPJEnvironmentVar> or array of TPJEnvironmentVar.

The definition of the TPJEnvironmentVarArray type can either be deleted or deprecated.

[delphidabbler]

This change affects the API and means demos have to be changed.

Leave the change until ready to update demos.

[delphidabbler]

I've created a new temporary host application so not having to compile the unit using a demo project as host.

API can now safely be broken without preventing compilation so renaming can go ahead.

Problems with broken demos can be fixed later (see issue #18).