Merge pull request #6 from uwescience/filter_test

Filter test
Moved sql files into inst subdirectory which will be installed with package.  This allows R code to create SQLite3 database.
Change the way that the project location and evt data locations are specified.  They can now be changed at runtime instead of install time.  Added a check for empty files in readSeaflow and changed an error exception to a warning exception.  Added functions to enable parallel filtering of a batch of EVT files using the R library snow.
Fixed a couple bugs related to db management
Added command to try to install new dependency snow.
Added functions to set cruise name and instrument location at runtime.
Fix bug where cruise.id wasn't exported properly to snow worder processes.
Merge pull request #7 from ctberthiaume/parallel-filter

Parallel filter
Merge commit '009dd4a118da08c40dc1a1cb3c65492cf9e9bf29' into filter_test