[doc][improvement] Add README.md in each Measure folder

[NG-GOM]

Documentations of measures are only accessible online, through the Wiki.
It's not at all convenient when working on an isolated environment, where there's no access to "the outside world".

Main advantages I see on using these README files :

• "Self-documentation" of the module : Having the module's directory is enough to have all the informations needed to understand what is it and how it's used ;
• "Human-readable" : The Markdown formatting is quite easy to write & read, so even on limited environments (servers accessed through SSH and a basic text tool like vim, cat, less,...) it is easily usable ;
• Maintenability : README.md are supported by Github, so the wiki could refer to the module's Github directory to display documentation instead of maintaining its own documentation of the module. It would avoid divergences between Wiki documentation and the current state of the module. For example, if a developer forks the project and changes the features of a module, he also can update the documentation accordingly before doing a pull request, thus reducing the work needed to maintain an up-to-date Wiki documentation. Plus, if you have an old revision of a module, you would still have access to its related documentation, as it is versionned with the sources.

It shall contain (non-exhaustive list) :

• A "Generalities" chapter containing :
  • A (small) introduction to the main project, link to project's website,...
  • A description of the module (a brief sentence + a detailed description)
  • A complete table describing environment requirements (MeasurePlatform version, if relevant : external tools versions,...)
• A chapter describing the build steps and requirements to generate the module from a reference environment
• A chapter describing the usage of the module (operationnal configuration, exploitation)