Re-organize repository folder structure

[vince-fugnitto]

Description

Propose to re-organize the repository's folder structure in order to better manage the increasing number of applications present in the repo.

Currently, all apps are currently present at the root of the repo but I suggest that we group them under the parent folders docker and electron in order to easily distinguish between the two types of apps.

Ex:

├── docker/
│   ├── theia-cpp-docker
│   ├── theia-full-docker
│   ├── theia-docker
│   └── theia-go-docker
└── electron/
    ├── theia-cpp-electron
    └── theia-electron

[dwjbosman]

I also suggest to support multiple docker image configurations per app. For example I am currently busy with a Theia image supporting Rust for embedded development.

├── docker/
│   ├── theia-cpp-docker
│   ├── theia-full-docker
│   ├── theia-rust-docker
│       └── general
│       └── embedded
│   ├── theia-docker
│   └── theia-go-docker
└── electron/
    ├── theia-cpp-electron
    └── theia-electron

[satishbabariya]

multiple variants of docker images would be great like slim or alpine (+1),
but for that, we need to update install script in .travis.yml to traverse into the subfolders, and for image tag can be named like follows

• latest
• next
• 0.10.0.x.x
• latest-alpine
• next-alpine
• 0.10.0.x.x-alpine

[marcdumais-work]

@dwjbosman I think we can start with your suggestion above
@satishbabariya I am not sure if we'll get these type of image variant for more than maybe the most basic image (e.g. theia-docker) - it can be a challenge to install extra tools with alpine and such. I propose we "cross that bridge" when we get there.