PRM: Start new Puppet 2.7 Reference Manual section
PRM: Begin breaking down the language guide into an organized, versionable reference

This commit breaks out and partially rewrites several sections of the language guide.
More to come.
Add scope chapter to Puppet reference manual
Minor copy edits
Copy edits to datatypes, defaults and reserved language guide pages.
Minor typos.
Merge remote-tracking branch 'fredlf/reference_manual' into reference_manual
prm: add containment section
PRM: run stages
PRM: Add language summary
PRM: Add node definitions section
PRM: Note that allowed node names are undefined behavior.
PRM: minor tweaks
PRM: Add section on conditional statements
PRM: Add section on expressions
PRM: Minor revisions
PRM: some minor changes based on read-throughs
PRM: Add import section
Copy edits to lang_conditional page.
Merge remote-tracking branch 'fredlf/reference_manual' into reference_manual