Support cp2k cell parsing in npt log file

[coveralls]

Pull Request Test Coverage Report for Build 6424662897

• 61 of 68 (89.71%) changed or added relevant lines in 7 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+1.2%) to 36.211%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cp2kdata/block_parser/cells.py	11	12	91.67%
cp2kdata/block_parser/md_xyz.py	4	5	80.0%
cp2kdata/dpdata_plugin.py	1	2	50.0%
cp2kdata/output.py	24	28	85.71%
<!--	Total:	61	68	89.71%	-->

Files with Coverage Reduction	New Missed Lines	%
cp2kdata/output.py	1	63.72%
<!--	Total:	1		-->

Totals
Change from base Build 6114149904:	1.2%
Covered Lines:	625
Relevant Lines:	1726

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💛 - Coveralls