Data export revision (#463)

* data export fixes

* added nan entry first

* updated stats

* added filter

* removed loader filter, as it can us char counts filter

* update size dist to list

* save export

* update load more flexibility

* updated header

* Update particula/data/loader.py

Co-authored-by: sourcery-ai[bot] <58596630+sourcery-ai[bot]@users.noreply.github.com>

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Co-authored-by: sourcery-ai[bot] <58596630+sourcery-ai[bot]@users.noreply.github.com>