[Data converter] Improve the hex parsing & general functionality

[EclecticGriffin]

I spent some more time hacking on this instead of spending my time in a more productive way. This does the following:

• switch the dat deserializing from custom matching stuff to a proper nom parser that accounts for comments and leading 0x tags.
• dat files can now parse values with leading zeroes truncated (though we continue to generate dat files with the leading zeroes included)
• Output dat files will be generated by default as MEMNAME.dat though this can be customized with -e flag. I.e. -e out will generate MEMNAME.out
• Similarly, when reading in a dat directory, the tool will look for MEMNAME.dat which can be retargeted via -e flag.
• The tool will also infer the --to json target when given a directory as input

[ekiwi]

Looks great! Thanks