Feature request: Interpolate one array, "re-use" weights on other arrays

In my code I need to interpolate many different arrays at the same points. A signficant part of my computation time is spent on interpolating, but I can cut the time down significantly if it would be possible to "reuse" interpolation weights and positions. The following example illustrates.

something not to different from this:

```Julia
## Create arrays, interpolation objects etc
xgrid = 1:1:10
ygrid = 1:1:10
array1 = [xgrid[ix] + 1*ygrid[iy] for ix=1:length(xgrid), iy = 1:length(ygrid) ]
array2 = [xgrid[ix] + 2*ygrid[iy] for ix=1:length(xgrid), iy = 1:length(ygrid) ]
array3 = [xgrid[ix] + 3*ygrid[iy] for ix=1:length(xgrid), iy = 1:length(ygrid) ] # Three arrays defined over the same grids
array1_intrp = LinearInterpolation((xgrid,ygrid),array1,extrapolation_bc=Line())
array2_intrp = LinearInterpolation((xgrid,ygrid),array2,extrapolation_bc=Line())
array3_intrp = LinearInterpolation((xgrid,ygrid),array3,extrapolation_bc=Line()) # Three interpolations objects

## Do lots of calculations that require calling the interpolation objects many times

for i = 1:1000 # big loop
i = 1
x = 10.0/i # Some values which depends on which iteration I am on
y = 10.0/i
val1 = array1_intrp(x,y)
val2 = array2_intrp(x,y)
val3 = array3_intrp(x,y)
val = function(val1,val2,val3) # some function that combines the three interpolated values
end

```

Now, the point is that since all of the interpolations are evaluated at the same values `(x,y)` and are "defined" on the same grids, we don't really need to do all the calculations to find `val2, val3`, since we can reuse the weights that were used in finding `val1`.

Then the question becomes:

1. Is this currently possibly? If yes, then
1.1 Is it possible to make interpolations.jl export the weights and closest grid points so that I can manually perfrom the interpolations from `val2,val3`?
1.2 Is there a way to tell interpolations to just interpolate three objects at the same time?
2. Is this something you would consider adding in the future?