Draft: construct pangenome database from GFA

Related to !147, I would like to not only go from pantools_DB -> GFA but also vice versa. This merge request collects my tries of doing that. It's marked as draft for now because I'm not sure if I'll use this code in the end.

TODO:

• Fix kmer index
• Make working on cyclic graphs
• Find out what happens with degenerate nodes
• Don't require genome locations file if GFA is provided (if GFA contains sequences)
• Get it to run on any valid GFA
• Ensure neo4j -> GFA -> neo4j gives identical database
• Ensure GFA -> neo4j -> GFA gives identical GFA file
• Update documentation accordingly

CHANGELOG.md

 All notable changes to Pantools will be documented in this file.
 
-## [UNRELEASED]
-
 ### Added
-- Available resources are now added to the log files and validated for some processes (!224).
 - The possibility to analyse a specific region of interest across the pangenome (!147).
 - A GFA export function (not speed optimised, so not recommended for large pangenomes) (!147).
 
 ### Changed
-- Added error catching for a set of pangenome node parameters that can cause issues down the line (!225).
 - Renamed the developer function `export_pangenome` to `export_csv` (!147).
 
+## [UNRELEASED]
+
+### Added
+- Available resources are now added to the log files and validated for some processes (!224).
+- Added error catching for a set of pangenome node parameters that can cause issues down the line (!225).
+
 ### Fixed
 - `pantools blast` no longer crashes if not all mrna nodes contain protein IDs (!226).
 - `pantools calculate_synteny ` now gives an exception if MCScanX runs out of memory (!226).