Reversed the validation of providers.

This is because it would break the 'serve' command.  Will do something
about this.  Also, a few small changes to the command line argument
parsing.
Improved the search queries.

Search queries are now full blown expressions.  Also added an invert,
urn only and value only switches.
Fixed harvesting from file.

Moved the file harvester into the set of pre-canned harvesters
supported.  Also fixed a bug in LinesInFile which was not producing any
lines in files.
Moved the list and get into a standard harvester.

The cmdharvester command is now only using standard harvesters.
Added back the -L and -F option for cmdsearch