Inserting and extracting FSAs from Array blocks

[c42f]

@awbsmith needs something for constructing FSAs from parts of a larger AbstractArray, but without allocating a temporary.

The main issue here is choosing the right name. slice and sub are right out due to 0.5 vs 0.4 compatibility. view seems like the right thing, with exactly the same syntax and semantics as Base.view in 0.5, but with an extra parameter to specify the output type:

view(Mat{3,3}, A, 1:3,1:3)   # produces Mat{3,3,eltype(A)}(A[1:3,1:3])

Symmetrically, we should also have the ability to set blocks in Arrays to a given FSA:

A[1:3,1:3] = eye(Mat{3,3,Float64})

[andyferris]

👍 to using the view(Type, array, indices...) syntax.