Fix python function to_netscape

[mahlzahn]

Although this function may be removed or better written in the rust library, currently it was just broken and this PR fixes it:

• fix correct reading of cookie dictionary values
• set https_only using the value of secure of the cookie
• set subdomain according to domain starting with .
• add prefix #HttpOnly_ to domain for http-only cookies

See, for instance, https://docs.cyotek.com/cyowcopy/current/netscapecookieformat.html for documentation of the netscape cookie format. The resulting cookies were also cross-checked with the output of

from http.cookiejar import MozillaCookieJar

mcj = MozillaCookieJar('/tmp/cookies')
for c in rookiepy.to_cookiejar(rookiepy.chromium():
    mcj.set_cookie(c)
mcj.save()

[thewh1teagle]

Thanks!