Parser improvements.

For files with multiple versions in the format TXC_2-AIRP-x-sj2.xml, the script will choose the current file as per https://tdx.131500.com.au/download/files/TransXchange_Data_Release_Notes_V_2_2_121018.pdf

Don't write unneeded files
Write needed data to one file (<filename>-data.json)
Add support for choosing files based on date
Added dependency on 'cat' and 'grep'. Sorry, Windows.