Shorthand for curried functions

I love partial application, especially in the presence of HOFs, but especially with the [long syntax for lambdas](https://github.com/google/jsonnet/issues/129) it's currently pretty heavyweight to write those. Even if the syntax were more lightweight, I believe the following could be quite nice:

```
local foo(params1)(params2) = ...;
```

as shorthand for:

```
local foo(params1) = function (params2) ...;
```

Given that we already have the `local foo(params) = ...` as sugar for `local foo = function(params) ...`, it seems like iterating the current rule for each group of parentheses would be a nice generalization of the syntax. Same would apply to object "keys", as well as anonymous functions.