Overloading Base.vect

Overloading `Base.vect(::Plot...)` (`[p1, p2]` syntax) to return a new `Plot` instance is really counter-intuitive and violates the contract of the function. The docstring is "Create a Vector with element type computed from the `promote_typeof` of the argument, containing the argument list" so I would expect this to at the very least return an `AbstractVector{Plot}` if not a `Vector`. This result is very unexpected if the user wants to create an actual vector of plots.

In my opinion, the methods for `vect`, `vcat`, and `hcat` should be removed so that they create the expected 1D or 2D array of plots, and there should be a specific function (or maybe just another method of `plot`) to combine them as subplots. This would be much more clear and explicit.