Modification of the structure to lammps format

[JPchico]

Addresses #41

Removing ase dependency on how the structure string is written.
Moving the parsing functions to the actual parser folder to make the structure cleaner.

[codecov]

Codecov Report

Merging #70 (23ba73f) into develop (0086836) will increase coverage by 4.02%.
The diff coverage is 84.61%.

@@             Coverage Diff             @@
##           develop      #70      +/-   ##
===========================================
+ Coverage    83.33%   87.36%   +4.02%     
===========================================
  Files           16       17       +1     
  Lines         1440     1369      -71     
===========================================
- Hits          1200     1196       -4     
+ Misses         240      173      -67     

Flag	Coverage Δ
pytests	87.36% <84.61%> (+4.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
aiida_lammps/parsers/utils.py	80.55% <60.00%> (ø)
aiida_lammps/parsers/parse_raw/final_data.py	76.92% <76.92%> (ø)
aiida_lammps/parsers/parse_raw/lammps_log.py	94.54% <94.54%> (ø)
aiida_lammps/calculations/base.py	97.24% <100.00%> (ø)
aiida_lammps/data/trajectory.py	90.74% <100.00%> (ø)
aiida_lammps/parsers/base.py	86.66% <100.00%> (ø)
aiida_lammps/parsers/inputfile.py	87.31% <100.00%> (ø)
aiida_lammps/parsers/parse_raw/__init__.py	100.00% <100.00%> (ø)
aiida_lammps/parsers/parse_raw/trajectory.py	79.22% <100.00%> (ø)

[JPchico]

Ping @chrisjsewell or @sphuber any comments? or ready to merge?