3.0.2-updates

The latest updates include:

- Major bug fix:
when creating NmrChain from a Chain (including after loading a FASTA file). This error created a compromised project which gave a `Fatal Error` when reloading it.

- Minor bug fixes:
for SpectrumGroups series non updating correctly.
various GUI flaws.

- New features:
Gradient colours for spectra and SpectrumGroups.
Merge NmrResidues and NmrAtoms from NmrResidueTable and ChemicalShiftTable context menu.