Implement a license clarity score

[pombredanne]

For use here and in ClearlyDefined, we should compute a license clarity score. The specification is documented in this ClearlyLicensed Metrics doc.

[pombredanne]

There are several elements in the scoring and these would leverage:

• whether a detected license is a full text, notice or mention When detecting a license report if a full license text, or only a notice or mention was detected #80 Improve reporting of the importance of detected licenses  #979 (available in develop branch)
• support for facets Proposal: high level file classification #426 and Define patterns of file names and types for classification #1036 (available in develop branch)
• whether a file is a key/legal/top level file or not.(see https://github.com/nexB/scancode-toolkit/blob/794c502ca64804f69c50585a20546188546bb125/src/summarycode/classify.py)
• and of course license and copyright detection and SPDX license support

[pombredanne]

Here is the status so far:
The latest doc link for license scoring https://docs.google.com/document/d/1o_VuVnP1PMoYOXZHSm0TyDX4CsqDXM3zqESAE0AoUnQ/edit#

And I have a working scoring implementation https://github.com/nexB/scancode-toolkit/tree/license-scoring

  "license_score": {
    "score": 82,
    "has_top_level_declared_licenses": true,
    "file_level_license_and_copyright_coverage": 0.9,
    "has_consistent_key_and_file_level_license": true,
    "has_all_spdx_licenses": false,
    "has_all_license_texts": true
  },

that's using facets:

  "scancode_version": "2.9.2.post351.e23b1d79f.dirty.20180916153557",
  "scancode_options": {
    "input": "dnsmasq-2.45",
    "--classify": true,
    "--copyright": true,
    "--facet": [
      "dev=*/bld/*",
      "examples=*/contrib/*",
      "docs=*.html",
      "examples=*.example",
      "data=*/po/*",
      "data=*/dbus/*",
      "docs=*/man/*",
      "docs=CHANGELOG",
      "docs=FAQ"
    ],
    "--info": true,
    "--json-pp": "<stdout>",
    "--license": true,
    "--license-clarity-score": true,
    "--processes": "3",
    "--summary": true,
    "--summary-by-facet": true
  },

[pombredanne]

This is completed and merged in develop