Avoid using FSharp.Core types in BigDeedle public API
Avoid using FSharp.Core types in BigDeedle public API

Using F#-specific types like lists in public API is a bad practice.

Also, this should resolve `TypeInitializationException` error that happens
because of different `FSharp.Core` version is referenced, but BigDeedle is
not actually used.

Conflicts:
	src/Deedle/Vectors/VirtualVector.fs

buybackoff/Deedle,filmor/Deedle,buybackoff/Deedle,buybackoff/Deedle,filmor/Deedle,caioproiete/Deedle,AtwooTM/Deedle,tpetricek/Deedle,AtwooTM/Deedle,tpetricek/Deedle,Dependencies/Deedle,jeyoor/Deedle,caioproiete/Deedle,BlueMountainCapital/Deedle,Dependencies/Deedle,BlueMountainCapital/Deedle,filmor/Deedle,AtwooTM/Deedle,caioproiete/Deedle,jeyoor/Deedle,BlueMountainCapital/Deedle,Dependencies/Deedle,jeyoor/Deedle,tpetricek/Deedle