packagesdb - Refactor out get_rdep_dict() from calc_rrdep_counts().

Also, cache the dictionary for performance.
packagesdb.py - Use get_package() in get_rdep_dict() to resolve virtual pkgs.

Along with some associated cleanup.
packagesdb - Add routine to calc rdep metrics by package as needed.
packagesdb - Add rdep metric accessors at the PackagesDB level.
Use the on-demand versions of the rdep metric calls.
packagesdb.py - Remove the Package-level interface for rdep metrics.
piuparts-report.py - Avoid sorting passed files by block count.

And refactor passed vs. failed sort handling.

There was still a case where a full accounting of rdep metrics was
called for - the sort of successfully-tested in piuparts-report.
Avoid the sort call to block_count if we know it is not going to
affect the sort.

With this change, piuparts-reports now runs at 35 seconds per section.
Changelog entry for rdep metric rework.
debian/changelog: move Dave's changes to 0.54
debian/changelog: Add Closes: for #705977
piupartslib/packagesdb.py - Add rdep chain length metric calc.

Provide a means for detecting packages which support a long chain
of reverse dependencies, so that testing priorities can concentrate
on whittling them down.

-------------------------------
piupartslib/packages.db - Prioritize by rdep chain len in reserve()

Use the rdep_chain_len metric to proportionally prioritize packages
returned by reserve() according to the length of the longest reverse
dependency chain length.
start with 0.54

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p: ignore (creation of) /etc/hosts

netbase 5.1 always creates /etc/hosts upon installation

Signed-off-by: Andreas Beckmann <anbe@debian.org>
merge andreas/for-bikeshed
enable ia32-libs workarounds for jessie

Signed-off-by: Andreas Beckmann <anbe@debian.org>
disable the /home check for squeeze-proposed

Signed-off-by: Andreas Beckmann <anbe@debian.org>
skip md5sums check if /usr/share/doc is pruned

avoid noise and ressource violation on sid-nodoc

Signed-off-by: Andreas Beckmann <anbe@debian.org>
install more recommended/suggested databases

Signed-off-by: Andreas Beckmann <anbe@debian.org>
README_server.txt: be more verbose about configuring sudo. (Closes: #711155)