Update submodule to latest commit, identify meta.txt/data.csv files

I fixed the code to update the submodule ipcc-fact-checking:
the previous code was meant to update the submodule in reaction
to a change of the upstream parent repository ipcc-facts-import.
Instead, updating the submodule required, from within the submodule
directory, to ensure that the master branch was selected and to pull
(fetch and merge) the latest changes into the master branch.

What is not included is the update of the parent repository
ipcc-facts-import to move the submodule reference to the latest
commit. This requires a commit in the parent module, which should
not be automated, but done manually by a human.

I also added code to locate meta.txt and data.csv within datasets
folder in ipcc-fact-checking, and to extract the source, document
and dataset identifiers (folder names) from the files's parent path.
Remove redundant semicolons at end of for in expression
Extract facts from meta.txt files

The processing of meta.txt files stops at the first empty line;
the description is discarded.

For the insertion of string literals in SQL, I used single quotes
(more standard) for all fields except the 'value', where I used
double quotes instead because I expect this field to contain
apostrophes (single quotes) occasionally. An alternative would
be to check and escape properly any single quote found in values.
Start to parse data.csv files, skip lines with no values
Rename add{Meta/Data}Fact(s) functions to parse{Meta/Data}{File/Line}
Provide headers line as second parameter to parseDataLine
Replace subshell call to expr with arithmetic expansion
Disable backslash escaping of end of lines in read lines (unneeded)
Parse fields to extract facts from CSV files
Reset headers for each CSV file

Previously, the headers of the first file were kept incorrectly
for all subsequent files. I replaced the test to check the value
of the line number instead of checking whether the variable is
initialized.