Content checks should be less verbose

[jcran]

See #8 as well, but this sort of verbosity around content checks is unnecessary. Save it for the JSON/CSV output. For the CLI, only print stuff that would be useful to a tester.

Specifically:

• remove location header
• remove security header info if they don't print something that can be actioned
• remove anything that's 'false'
• remove email addresses output if there are none.

Checking URL: http://127.0.0.1/
Checking... http://127.0.0.1/
Fingerprint:
 - Apache HTTP Server 2.4.41  - Apache web server - server header - with versions (CPE: cpe:2.3:a:apache:http_server:2.4.41:) (Tags: ["Web Server"])
Content Checks:
 - Access-Control-Allow-Origin Header: false
 - P3P Header: false
 - X-Frame-Options Header: false
 - X-XSS-Protection Header: false
 - Google Analytics Account Detected: false
 - Location Header: 
 - Directory Listing Detected: false
 - Form Detected: false
 - File Upload Form Detected: false
 - Email Addresses Detected: []
 - Authentication - HTTP: false
 - Authentication - Session Identifier: false````

via @bcoles 

[jcran]

CAlling this done