FreeSWITCH-codec2

Allow setting format of log filename in format_cdr

This commit allows you to set a `log-file` string parameter in a
format_cdr profile.  This string is a template that may (and should!)
contain variables.  This template will be expanded and used as the
file name of the CDR to be written.  This parameter should contain
only the template for the file name itself; the path is relative to
the `log-dir`.