Prototype for magic numbers

[SimonDanisch]

Hi, what do you all think of this way of loading and registering file extensions?
https://github.com/JuliaIO/FileIO.jl/blob/master/src/core_prototype.jl
It's just a crude prototype by now:

# Example taken from MeshIO
#Registering a file format
#Mime(unique_identifier, file_ending, magic_number)
const ply_binary = Mime(:ply_binary, :ply, b"ply\nformat binary_little_endian 1.0\n")
const ply_ascii  = Mime(:ply_ascii,  :ply, b"ply\nformat ascii 1.0\n")

file = file"test_ascii.ply" #just wraps the path in the file type
obj = load(file) # tries to find mime and opens io stream and returns appropriate julia object
obj = load(file, GLNormalMesh) # tries to return a GLNormalMesh while loading
obj = GLNormalMesh(file) # just works if defined in the mesh package, as call(::Type{Any}, ::File) leads
# to millions of ambiguity warnings

this is heavily inspired by the approach taken in Images.jl ( I'm not sure who wrote this particular code, but probably @timholy can say something about this)

Best,
Simon

[timholy]

Closed by #15