Better error-checking; ptoids field; tweaked usage

By default, intermediate files will NOT be removed unless the `cleanup` action is given on the command line.

Existing .zip files will NOT be re-downloaded; processing will continue as if the download had occurred.

If a download is interrupted, the partial .zip file is removed.

Anything can be passed as arguments on the command line; anything which isn't an action or a ipa/ipg file will be ignored.  This lets the user copy-and-paste a segment of the PTO webpage into a file and run a command like:
```
prompt> cat webtext.txt | xargs processFile.rb download
```
and the incidental garbage test will be ignored.

A `.gitignore` file has been added to reduce `git status` clutter from intermediate and temp files.

A new `ptoids` column has been added to hold values extracted from the `govint` field.  THIS IS CURRENTLY EXPERIMENTAL AND SHOULD NOT BE TRUSTED TO BE CORRECT.

A new tool has been made to justify the column widths of a csv file:
```
fixCsvCols.rb csvfile > out.txt
```
The `out.txt` file will have fixed-width columns fitting their contents/header widths.