Fix sail docker and upgrade code-server

[dougnukem]

• Fixes cosmic no longer supported (EOL) #250 issues with ubuntu 18.10 base docker image, upgrade to ubuntu 20.04 LTS (will be supported for a good while)
• Fixes sail command retrieve wrong version of code-server #260 Fixes Failed to Build image, Exit 100 #261 issue with sail using latest code-server which now supports ARM64 and X86 architectures

It now appears to work

$ cd sail/images
# Rebuild base image
$ ./main.sh
# Rebuild golang image
$ ../buildlang.sh ubuntu-dev-go
# Tag for local docker images
$ docker tag ubuntu-dev-go:latest codercom/ubuntu-dev-go:latest
# Rebuild sail and run
$ go install && sail -v run --keep dougnukem/sail
Successfully built 22e42f37c091
Successfully tagged dougnukem_sail:latest
2020-03-10 15:40:03 INFO	using repo image dougnukem_sail
2020-03-10 15:40:03 DEBUG	host home dir: /Users/douglasdaniels
2020-03-10 15:40:03 INFO	writing sail proxy logs to /var/folders/ht/gwk63jw55_b_kpkk3jf599r40000gn/T/sailproxy_dougnukem_sail209919673
2020-03-10 15:40:03 DEBUG	started container
2020-03-10 15:40:04 DEBUG	code-server online
2020-03-10 15:40:04 INFO	please visit http://127.0.0.1:62686

Open Issues

I needed to disable the installation of the docker vs-code extension as it can't be resolved using code-server for some reason, it looks like the namespace changed recently (https://marketplace.visualstudio.com/items?itemName=ms-azuretools.vscode-docker):

Installing extensions...
Extension 'ms-azuretools.vscode-docker' not found.
Make sure you use the full extension ID, including the publisher, e.g.: ms-vscode.csharp
error vscode undefined
The command '/bin/bash -c installext 'ms-azuretools.vscode-docker'' returned a non-zero code: 1
2020-03-10 15:39:15 FATAL	failed to build image: failed to build: exit status 1

[dougnukem]

/cc @deansheather

[deansheather]

Note to self: once this is merged I'll need to rebuild all of the sail images and push them to docker hub

[dougnukem]

@deansheather resolved feedback, should be ready

[deansheather]

Thank you for your contributions. I'll push the changes to docker hub shortly.