Rename every source.txt to meta.txt
Add year, tags to each metadata file

I also added explicit names to each field,
in the format 'Key: value' on one line
except the description field, which starts
with 'Description:' after an empty line,
and extends to the end of the file.
Add data extracted from ipcc_far_wg_I_app_02.pdf
Add rule to ignore OpenOffice lock files
Rename 'Organization' field to 'Group', more generic
Rename remaining source.txt files to meta.txt
Add year, tags, and reformat remaining metadata files
Add data extracted from ipcc_far_wg_I_app_03.pdf