Component manager - Improve components_available.json

[chaveiro]

This file https://github.com/openenergymonitor/EmonScripts/blob/658d982aa968076071d46df87ab9174d3c9df1e7/components_available.json is used directly from Modules/admin/admin_model.php components_available() function at the follow address:
https://raw.githubusercontent.com/openenergymonitor/EmonScripts/stable/components_available.json

Suggest to add :

• description -> optional text that appear on the component module list
• branches_available -> optional install branches
• isModule -> true if it's a standard emoncms module
• install_path -> optional location if installation is not %emon_path%/modules Dont use hard coded absolute paths, use template like %var% that gets replaced by installation script to accommodate different servers.

Example:

{
  "emoncms":{
    "name":"Emoncms Core",
    "description": "Some text about this module that appear on the component module list",
    "url":"https://github.com/emoncms/emoncms.git",
    "branches_available ": {"master", "stable"},
    "install_path": "%emon_path%",
    "isModule": false
  },
  "app":{
    "name":"App",
    "url":"https://github.com/emoncms/app.git",
    "description": "Some text about this module that appear on the component module list",
    "branches_available ": {"master", "stable"},
    "install_path": "",
    "isModule": true
  }
}

emoncms/emoncms#1732

[borpin]

@chaveiro - this seems to have been incorporated into the new 'Components' section of the admin interface. Can this be closed as a result of that?