Greenworks v0.8.0 for NW.js v0.18.8 & v0.19.4

• Greenworks complied for NW.js v0.18.8 & v0.19.4 with Steamworks SDK 1.38a
• Greenworks now requires libsdkencryptedappticket library. Plese copy it to
  the directory of your game.
• Update to Steamworks SDK 1.38a, thanks to @MadSpyxFR, some changes from
  Steamworks SDK:
  • SteamFriends suggest relationship type now is deprecated
  • greenworks.getCloudQuota returns a String representing 64 bits integer
• Add greenworks.deleteFile API, thanks to @dfabulich
• Add greenworks.getAppId API
• Add APIs for ticket decryption:
  • The ticket in greenworks.getAuthSessionTicket and
    greenworks.getEncryptedAppTicket callback is a Buffer type
  • greenworks.decryptAppTicket
  • greenworks.isTicketForApp
  • greenworks.getTicketIssueTime
  • greenworks.getTicketSteamId
  • greenworks.getTicketAppId
• Fix: potential issues causing by mismatched new/delete usage