Extract improvement operations from RedHat importer

[pombredanne]

The RedHatImporter does a lot of extra, not-immediately-needed, improvement-like work
In particular, we collect extra CVE details, Bugzilla and CVRF data too early. @ziadhany found out that with profiling we spend most of the time in doing network calls for these:

• Collect RedHat CVE json details that contain extra data as an improver, not an importer
• Collect RedHat Bugzilla details that contain extra data as an improver, not an importer
• Collect RedHat CVRF RHSA details that contain extra data as an improver, not an importer

[DennisClark]

the extra data may not be necessary