Replace ToolBox mnemonics by extra_data aliases

The extra_data aliases are similar to the ToolBox mnemonics, but they are proposal dependent, with the advantage of easily add sources on the fly during a beamtime.

There is no handling of the extra dimensions names by the aliases, so a solution for this still needs to be found.

We would need to:

• generate a default extra-data-aliases.yml based on the current mnemonics: @mercadil
• have a mechanism to deploy a default extra-data-aliases.yml file in the {}/usr folder of a proposal during the installation of the ToolBox environment: @carinanc
• copy the default alias file to all existing proposals (for compatibility when not using the environment of the proposal): @carinanc
• change the code in the ToolBox to use aliases: @mercadil
• Update the documentation, with an example of adding a source on the fly: @mercadil

The default extra-data-aliases.yml file should be part of the ToolBox and updated after each beamtime.

@lleguy