Add downloads page for the custom Ice builds (rebased onto develop)



This is the same as gh-108 but rebased onto develop.

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This PR adds a downloads page for the custom Windows Ice packages. The build can be tested on `necromancer` with

```
RELEASE=3.5.1 make ice
```

The output of this page is manually deployed to http://downloads.openmicroscopy.org/ice/3.5.1/