Extend table to support arbitrary vector types

Change from this

```julia
struct Table{T,P} <: AbstractVector{Vector{T}}
data::Vector{T}
ptrs::Vector{P}
end
```
to this

```julia
struct Table{T,Vd<:AbstractVector{T},Vp<:AbstractVector} <: AbstractVector{Vector{T}}
data::Vd
ptrs::Vp
end
```