Parse & analyse LICENSE files

[msrcodes]

Is your feature request related to a problem? Please describe.
Many projects ship with a LICENSE file, detailing the terms of the license for that project. This will often be the same as the license specified in package.json, but:

• The LICENSE may not be the same as the one in package.json
• The LICENSE file may exist, but the license attribute in package.json may not
• The license attribute may exist, but the LICENSE file may not

Describe the solution you'd like
Per stated issues above:

• The LICENSE may not be the same as the one in package.json
  This should be flagged as an error in the console for esnecil list. Having two stated licenses should require manual intervention.
• The LICENSE file may exist, but the license attribute in package.json may not
  In this case, state that the tool has parsed the LICENSE file and use this data to inform data as usual. If both are missing, assume NO_LICENSE.
• The license attribute may exist, but the LICENSE file may not
  This is fine, we can ignore this case.

Describe alternatives you've considered
Not doing this: a risk, for reasons stated above

Additional context
LICENSE files aren't standardised, unsure of approach