Installation doc: add remark on RHEL Perl

On RHEL based platform, the Perl RPM does not contain all core Perl
modules of a Perl release. Users should request their site admin to
install Perl-Core.
Merge pull request #75 from matthewrmshin/doc-install-rhel-perl-remark

Installation doc: add remark on RHEL Perl
fcm make: doc: Clarify use of target names as namespaces + fix typos
Merge pull request #76 from dpmatthews/fcm-make-doc-fix

fcm make: doc: Clarify use of target names as namespaces + fix typos