Create a Windows installer for ImageJ2/Fiji

Nobody has claimed this yet.

Right now, Fiji and ImageJ2 have the problem that if unpacked into the `Program Files` directory on Windows, the ImageJ Updater does not have full, unimpeded read/write access to its own directory. This is due to the Windows security model. It is in general very difficult to detect programmatically whether things will work; they might seem to work temporarily until the computer is rebooted, for example.

However, there is a potential solution: distribute the Windows version of ImageJ using an installer such as NSIS or Inno Setup, and have the installer flag the entire ImageJ/Fiji directory as globally writable by all users.

For details, see [this SO answer](http://stackoverflow.com/a/8486370) and [this Inno Setup FAQ entry](http://www.jrsoftware.org/isfaq.php#perms).

Having a Windows installer will be good anyway because Windows users are most comfortable with them (just like OS X users are comfortable with DMG images which they mount and then copy the .app into `/Applications` themselves).

One wrinkle is that we still want to give a helpful error message if ImageJ/Fiji was manually unpacked into `Program Files` _without_ using the installer. To do that, we can have the installer write a stub file into the installation directory, which is not present in the ImageJ/Fiji cross-platform zip distribution. And if the Updater does not see that stub file, it refuses to try to update an installation in `Program Files`.

Migrated-From: http://trac.imagej.net/ticket/2011

Start by investigating the Windows distribution and ImageJ Updater entry points, then compare the proposed NSIS or Inno Setup approaches. Done means a Windows installer provides writable installation permissions, writes the installation stub, and the updater gives a helpful error for unpacked installations under Program Files.

Written by the indexing model from the issue text.