Support for working on multiple SAFE projects in parallel

[theimowski]

Splitting #113
Issue is that one cannot have multiple instances of apps created from SAFE template in run mode

This is due to:

• fable default port 61225
• hardcoded port 8080 for web server
• hardcoded port 8085 for webpack

[matthid]

Actually let me clarify: I wouldn't mind if this scenario would NOT be supported. But I mind that the current behavior is just a full lock and I have to kill everything and start from scratch (I wouldn't mind the second instance failing if the first instance continues to work for example)

[theimowski]

Right, anyway I imagine it'd be a similar effort to allow multiple instances working in parallel, so I'd opt for that.
If it turns out hard in practice, then we can fallback to block

[theimowski]

As an afterthought IMO it's unlikely one desperately needs a scenario to work on multiple SAFE projects in parallel.
As of now, if one tries to run a second project, the errors are quite clear what's wrong:

Client:

events.js:167
      throw er; // Unhandled 'error' event
      ^

Error: listen EADDRINUSE 127.0.0.1:8080

Server:

crit: Microsoft.AspNetCore.Server.Kestrel[0]
      Unable to start Kestrel.
System.IO.IOException: Failed to bind to address http://0.0.0.0:8085: address already in use. ---> Microsoft.AspNetCore.Connections.AddressInUseException: Address already in use ---> System.Net.Sockets.SocketException: Address already in use

[matthid]

No the problem was different. As far as I remember it didn't even compile becahse it was trying to connect with the wrong fable compilation service and 'hang' forever, that's why I reported this initially

[theimowski]

Right, anyway looks like with current version of fable the behaviour is different and as a result this shouldn't be a huge issue. Running first project still works even if you try to run a second project and fail to