(doc) Fix a typo in docs for the include function

There is a typo in the documentation for the include function.
This patch merely fixes that typo.
(maint) Banish "configuration parameter"

They are called settings!

Note: Two spec files relied on the wording of an error message I changed.
I revised them to find the new wording.
Merge pull request #2386 from joshcooper/issue/master/1707-erb-encoding

(PUP-1707) Ensure ERB generated help content is UTF-8 encoded
(PUP-1707) StringIO#set_encoding doesn't exist in ruby 1.8

Only call the method if the object responds to it.
Merge pull request #2365 from alexharv074/fix_typo_in_include_doco

(doc) Fix a typo in docs for the include function
Merge pull request #2368 from nfagerlund/maint_configuration_parameter

(maint) Banish "configuration parameter"
(pup-1766) Remove duplicate test
(pup-1766) Add support for multiple defaultfor's

Prior to this change, it was possible to specify a defaultfor to
cover, say, multiple osfamily's e.g. with:
    defaultfor :osfamily => [:os1, :os2]
Or it was possible to specify a more complex hash, e.g. with
    defaultfor :osfamily => :os1, :operatingsystemmajorrelease => "42"

But if more specificity for just one of the operatingsystem values was
needed defaultfor couldn't support that. This change allows for this, e.g.:
    defaultfor :osfamily => :os1  # all variants of os1
    defaultfor :osfamily => :os2, :operatingsystemmajorrelease => "42"  # only release #42 of this os

To support this change Provider defaults is now an array of hashes (formerly,
it was a merge of the hashes provided by all defaultfor invocations), which requires
commensurate updates to the dochook.

There are also some new spec tests for representative defaultfor combinations, and
two spec tests needed to be updated with the expectation that Facter will be invoked
to assess defaultprovider specificity.
(pup-1766) Set systemd as a default provider for the service type on rhel7