Improve tracing of curve in SVG files

[DunklesArchipel]

Some curves were not traced properly in Inkscape. Corners and edges should be removed. Some of the following files might be ok. Cross-checking does not hurt...

• alves_2011_electrochemistry_6010 (see Adapt metadata to latest svgdigitizer website#136)
• briega-martos_2021_cation_48 (see Adapt metadata to latest svgdigitizer website#136)
  • Check again
• endo_1999_in-situ_19 (see Adapt metadata to latest svgdigitizer website#136)
• engstfeld_2018_polycrystalline_17743 (see Adapt metadata to latest svgdigitizer website#136)
• gomez-marin_2012_surface_558 (see Adapt metadata to latest svgdigitizer website#136)
• hamad_2003_electrosorption_211 (see Adapt metadata to latest svgdigitizer website#136)
• horswell_2004_a_10970 - 3 - (see Adapt metadata to latest svgdigitizer website#136)
• jovic_1999_cyclic_247 - 7 - (see Adapt metadata to latest svgdigitizer website#136)
• kerner_2002_measurement_2055 - 9 - (see Adapt metadata to latest svgdigitizer website#136)
• li_2000_chronocoulometric_95 - 4
• lipkowski_1998_ionic_2875 - 4
• mello_2018_bromide_18562 - 18
• mello_2018_understanding_J3045 - 32
• nakamura_2011_structure_165433 - 5
• nakamura_2014_structural_22136 - 1
• ocko_1997_halide_55 - 1
• pajkossy_1996_impedance_209 - 10 (see Entry fixes #150)
• pajkossy_2001_double_3063 - 3
• rehim_1998_electrochemical_1103 - 1
• shi_1996_chloride_225 - 4
• wandlowski_1996_structural_10277 - 2
• wang_1997_lateral_1 - 3
• wang_1996_ordered_6672 - 1
• zei_1991_the_295 - 2