document where cp.cache_file puts the file

It pulls it form the master and places it in the minions cache for usage
later.
Not that pillar is not used in state.orchestrate

in 2014.1 and before
begin adding function arguments to file module
expand documentation around sfn

This important variable is not documented anywhere else.  It is the
location in the cache where the minion recieves the file from the master
and then templates it or just moves it into place on the minion using

    try:
        salt.utils.copyfile(sfn,
                            real_name,
                            __salt__['config.backup_mode'](backup),
                            __opts__['cachedir'])
Merge pull request #14117 from gtmanfred/docsprint1

First set of patches for documentation sprint