Remove DataValueInterfaces code

Author: quinnj

src/DataAPI.jl

@@ -63,52 +63,6 @@ default definition.
 function refpool end
 refpool(A::AbstractArray) = nothing
 
-"""
-    nondatavaluetype(T)
-
-For a type `T`, return the corresponding non-`DataValue` type, translating between
-`Union{T, Missing}` and `DataValue{T}`.
-
-For example, `nondatavaluetype(Int64)` returns `Int64`, while
-`nondatavaluetype(DataValue{Int64})` returns `Union{Int64, Missing}`.
-
-This generic function is owned by DataAPI.jl itself, which is the sole provider of the
-default definition.
-"""
-function nondatavaluetype end
-
-nondatavaluetype(::Type{T}) where {T} = T
-nondatavaluetype(::Type{Union{}}) = Union{}
-
-"""
-    datavaluetype(T)
-
-For a type `T`, return the corresponding `DataValue` type, translating between 
-`Union{T, Missing}` and `DataValue{T}`.
-
-For example, `datavaluetype(Int64)` returns `Int64`, while
-`datavaluetype(Union{Int64, Missing})` returns `DataValue{Int64}`.
-
-This generic function is owned by DataAPI.jl itself, which is the sole provider of the
-default definition.
-"""
-function datavaluetype end
-
-datavaluetype(::Type{T}) where {T} = T
-datavaluetype(::Type{Union{}}) = Union{}
-
-"""
-    unwrap(x)
-
-For a value `x`, potentially "unwrap" it from a `DataValue` or similar container.
-
-This generic function is owned by DataAPI.jl itself, which is the sole provider of the
-default definition.
-"""
-function unwrap end
-
-unwrap(x) = x
-
 """
     describe(io::IO, x)
 

test/runtests.jl

@@ -27,24 +27,4 @@ end
 
 end
 
-@testset "nondatavaluetype" begin
-
-    @test DataAPI.nondatavaluetype(Int64) == Int64
-    @test DataAPI.nondatavaluetype(Union{}) == Union{}
-
-end
-
-@testset "datavaluetype" begin
-
-    @test DataAPI.datavaluetype(Int64) == Int64
-    @test DataAPI.datavaluetype(Union{}) == Union{}
-
-end
-
-@testset "unwrap" begin
-
-    @test DataAPI.unwrap(1) == 1
-
-end
-
 end # @testset "DataAPI"