Refactor package towards 1.0.0 release

[obackhouse]

This PR refactors the entire package in the interest of releasing as 1.0.0.

Whilst the general structure and idea remains the same, there are API changes throughout the entire project, and some features have been entirely reworked. Some notable changes are

• Transposition bug fixed in CCSD moment expressions s.t. zeroth order central GF moment is identity.
• FCI chemical potential now does not include e_ci, s.t. default value is 0.0 rather than e_ci.
• MBLGF and MBLSE are no longer combined with the MixedMBL__ classes, rather via Spectral objects.
• Static solvers now provide SE and GF via solver.result, which is a Spectral object.
• Dynamic quantities are now expressed using grid objects in dyson.grids
• Moment conversion and Lehmann.diagonalise_matrix work with non-identity zeroth order GF moments.
• Expression collections have different keys than "1h", "1p", with multiple valid keys for each:
  • Occupied: "ip", "o", "h", "hole"
  • Virtual: "ea", "v", "p", "particle"
  • Central: "dyson", "central"
  • Neutral: "ee", "ph", "neutral"
• Logging is now via rich and not logging. For globally disabling printing, call dyson.quiet().
• KPMGF has been removed for now, it's worse than CPGF and only gets the imaginary part of the GF.
• Lehmann is now in the dyson.representations module along with Spectral, and the new Dynamic, the latter being a container for dynamic GFs and SEs.