(FACT-599) Don't hardcode location of `sysctl`

`sysctl` is found in `/sbin` on OpenBSD but is in `/usr/bin` on OSX.
Because we can't assume the location it's easier to allow
`Facter::Core::Execution.which` to locate the executable to invoke.
Merge pull request #704 from adrienthebo/bugfix/facter-2/fact-599-sysctl-path

(FACT-599) Don't hardcode location of `sysctl`
(FACT-601) Format plaintext output for non-string values

Without this commit, structured facts outputted as plaintext are
printed using `#to_s`, which is useless on ruby 1.8.7:

    $ facter partitions
    sda1mount/bootsize1024000uuid7de786a9-be75-4711-b782-fb26aec963d4sda2size975747072sda3size2047

This commit changes the outputting to format non-string values using
`#inspect` which produces much more usable values:

    $ facter partitions
    {"sda1"=>{"uuid"=>"7de786a9-be75-4711-b782-fb26aec963d4", "size"=>"1024000", "mount"=>"/boot"}, "sda2"=>{"size"=>"975747072"}, "sda3"=>{"size"=>"2047"}}
Merge pull request #705 from adrienthebo/bugfix/facter-2/fact-601-structured-facts-plaintext-output

(FACT-601) Format plaintext output for non-string values
(RE-1497) Remove quantal from build_defaults

This commit removes quantal from all build defaults because it is end of
life. It removes the defaults from the build_defaults yaml.
(FACT-570) Pin facter to vendored ruby and ffi'ed gems on Windows

The acceptance setup step did not specify which revision of the vendored
ruby to install, relying on the default branch.

This commit makes it explicit as facter-2 depends on ffi-based windows
gems that are only available in the 1.9.3-x86 branch.
Merge branch 'facter-2' into stable
Merge branch 'stable' into facter-2
Merge branch 'facter-2'

Conflicts:
	lib/facter/util/posix.rb
(maint) Resolve conflict markers in lib/facter/util/posix.rb
Merge pull request #706 from clantant/RE-1497/master/srcs

(RE-1497) Remove quantal from build_defaults
(RE-1497) Remove quantal from build_defaults

This commit removes quantal from all build defaults because it is end of
life. It removes the defaults from the build_defaults yaml.
Merge branch 'stable' into facter-2
Merge branch 'facter-2'
(FACT-606) Remove Sid/Unstable from build defaults

This commit goes through the build_defaults.yaml and removes the sid and
unstable entries. Part of the reason for this removal is the lack of
testing the build but still shipping the packages and we already
build against Debian tests.