Reorganise components repository for readability.

There are over a dozen subprojects in the components repository and we can probably expect that to explode as more components and services are added.

We should introduce a directory structure to help navigate and build related modules in the system, and the documentation of the repository should be updated to help newcomers navigate the component framework.

It looks like the consensus is:

• `/core`
• `/services`
• `/components`
• `/examples`

We also had `build-tools` as a root directory, but where possible we should refer to http:github.com/Talend/tools.