DRILL-7626: Add ability to set HTTP response headers
1. Created ResponseHeadersSettingFilter for adding configured values to each response.
2. Now for when drill.exec.http.ssl_enabled users can add following headers
to improve security:
"X-XSS-Protection" : "1; mode=block",
"X-Content-Type-Options" : "nosniff",
"Strict-Transport-Security" : "max-age=31536000;includeSubDomains",
"Content-Security-Policy" : "Content-Security-Policy": "default-src https:; script-src 'unsafe-inline' https:; style-src 'unsafe-inline' https:; font-src data: https:; img-src data: https:"
