accept vectors for starting values

[mlubin]

Proposed in #477, this should work:

@variable(m, x[1:16], start = xstart)

CC @tyleransom

[mlubin]

Just to put some ideas down, we can take an array as a starting value under the following conditions:

• The variable is a OneIndexedArray
• The term xstart doesn't depend on any of the indexing variables in the definition of x
• If the above is true, we can check if the dimensions of xstart match the dimensions of x

[joehuchette]

👍

[mlubin]

Post 0.10 I think.

[dpo]

👍

[mlubin]

Given that you can just do:

@variable(m, x[1:16])
setvalue(x, xstart)

I'm not really convinced that we need to implement this feature. I think it's too magical to have the interpretation of the keyword arguments depend the fragile conditions I listed above.