Move command begin to C except when it must be called after another command in Perl (e.g. expire after backup). Command begin logs correctly for complex data types like hash and list. Specify which commands will log to file immediately and set the default log level for log messages that are common to all commands. File logging is initiated from C.
* Remove --reset tags from v1 options.
* Use constants for repo prefix.
* Specify CFGDEF_INDEX_PG in option structure rather than adding in code.
* Fix error message references to "backup host".
Contributed by Cynthia Shang.