Add support for building a single executable for Windows

[Lazza]

When building for Windows, sometimes it is desirable to include everything in a single .exe file rather than having a directory full of files. This PR leverages electron-builder to provide this option.

The build process runs just fine under macOS and Linux as well (Wine is downloaded and cached as needed).

Warning: for this to work, the favicon.ico can be a multiple-size version and it must include one version of at least 256x256 size.

[Lazza]

An additional note that might be useful to someone: when running as a single EXE, the app is actually unpacked to a temporary directory so it runs from a different working directory. To figure out the directory containing the compressed portable app, you can do something like this:

var environment = require('process').env;
var pwd: string = environment["PORTABLE_EXECUTABLE_DIR"] || environment["PWD"];

[rm-code]

The build process runs just fine under macOS and Linux as well (Wine is downloaded and cached as needed).

@Lazza I just tried packaging for windows via npm run electron:windows, but I get an error saying I don't have wine installed.

{ Error: Could not find "wine" on your system.

Wine is required to use the appCopyright, appVersion, buildVersion, icon, and 
win32metadata parameters for Windows targets.

Make sure that the "wine" executable is in your PATH.

See https://github.com/electron-userland/electron-packager#building-windows-apps-from-non-windows-platforms for details.
    at exports._errnoException (util.js:1020:11)
    at Process.ChildProcess._handle.onexit (internal/child_process.js:197:32)
    at onErrorNT (internal/child_process.js:376:16)
    at _combinedTickCallback (internal/process/next_tick.js:80:11)
    at process._tickCallback (internal/process/next_tick.js:104:9)
  code: 'ENOENT',
  errno: 'ENOENT',
  syscall: 'spawn wine',
  path: 'wine',
  spawnargs: 
   [ '/Users/rmcode/Coding/RemateClient/node_modules/rcedit/bin/rcedit.exe',
     '/var/folders/b2/s7g7mh7918nfyr9kgff752_40000gn/T/electron-packager/win32-ia32/remate-client-win32-ia32/remate-client.exe',
     '--set-version-string',
     'FileDescription',
     'remate-client',
     '--set-version-string',
     'InternalName',
     'remate-client',
     '--set-version-string',
     'OriginalFilename',
     'remate-client.exe',
     '--set-version-string',
     'ProductName',
     'remate-client',
     '--set-file-version',
     '0.0.0',
     '--set-product-version',
     '0.0.0',
     '--set-icon',
     'src/favicon.ico' ] }

[Lazza]

@rm-code the command I proposed with this PR is called winportable. The windows command is the "old" one which uses a different build tool.

[rm-code]

My apologies ... I was going by the docs in https://github.com/maximegris/angular-electron#included-commands and didn't think to check the contents of your PR. It worked fine with the winportable flag 👍

[Lazza]

No problem. 😄 Just keep in mind that electron-builder caches Wine inside $HOME/Library/Caches/electron-builder amounting to a whopping 240 MB.