Add support for reading and dumping multi-frames for gro file & add dump system to gaussian input file

[Ericwang6]

1. Support read from and dump to .gro file for multi-frame system
2. Add function to write gaussian input file (.gjf) with system's coordinates

[codecov-commenter]

Codecov Report

Merging #145 (471de61) into devel (f150dd1) will decrease coverage by 0.42%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##            devel     #145      +/-   ##
==========================================
- Coverage   84.98%   84.56%   -0.43%     
==========================================
  Files          28       28              
  Lines        3210     3375     +165     
==========================================
+ Hits         2728     2854     +126     
- Misses        482      521      +39     

Impacted Files	Coverage Δ
dpdata/gromacs/gro.py	98.75% <100.00%> (+0.83%)	⬆️
dpdata/system.py	80.34% <100.00%> (-0.32%)	⬇️
dpdata/md/water.py	44.00% <0.00%> (-4.19%)	⬇️
dpdata/cp2k/output.py	98.04% <0.00%> (-0.25%)	⬇️
dpdata/md/rdf.py	0.00% <0.00%> (ø)
dpdata/xyz/quip_gap_xyz.py	93.16% <0.00%> (+0.05%)	⬆️
dpdata/periodic_table.py	95.34% <0.00%> (+0.90%)	⬆️
dpdata/qe/scf.py	96.90% <0.00%> (+1.07%)	⬆️

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