Namespacing in command_names

[lenaxus]

At the moment it is only possible to run commands in the self-created "dev_cmds" directory.

When running a task with devmd it is only searching in the "dev_cmds"-directory, not in subdirectories. It could therefore be possible that with many self-created tasks it is difficult to structure the tasks.

This issue should adress this problem with the expansion of the namespace of the commands. The easiest way should be this suggestion:

• It should be possible to save commands in subdirectories. With this approach every user can structure his commands and gets the overview.
• When running a task with devcmd the script-name is no longer a single file-name. It is a path to the file starting in the "dev_cmds"-directory. This path can be build with slashes or colons. So for example it can look like this when I am trying to run the task foo in a subdirectory tutorial: 'yarn devcmd tutorial/foo'.