kea-admin lease-dump mysql

Part of #2038 (closed).

• 5ff94f94 kea-admin lease-dump mysql outputs a memfile-ready CSV
  • A disadvantage of the solution in here is that we lose the human-readability of the previous lease-dump command. I've pondered and I slightly tilt in favor of it. The alternative of having an additional command would confuse the user as to when to use one or the other. I initially added an additional command and that work is under branch 2038-lease-export.
• f27bf71a kea-admin lease-dump mysql tests
  • I found that some addresses added as integers in the lease6 table in other tests than the ones I added or modified, are not properly loaded by Kea. While inserting integers works for v4, the v6 column is a varchar so MySQL converts the integer to string as-is and Kea tries to load it and fails because e.g. 111 is not a valid IPv6 address. Just so you know why I modified those tests. If I'm wrong, I would happily revert.
• 9fead0ce document kea-admin lease-dump
• 4ac9d6ff add ChangeLog entry
• d8d07b93 kea-admin lease-dump mysql -6 now takes hwtype & hwaddr_source into account