Pynabi

* Fix: `CanDelay` in same dataset of one of its `Delayed` properties must delay that property
* Feature: you can now append stampable to groups of datsets to cut down repeated code

* __Breaking__: refactor of `kspace` -> there are now three specialized (mutually exclusive) classes `ManualGrid`, `SymmetricGrid`, `AutomaticGrid`, `Path`
* Refactor using `IndexedWithDefault` to cut down boilerplate code
* Refactor of the delaying code: `DelayedInfo` has been added and a delayed value now can be of type different from input
* `SCFDirectMinimization` does not take steps as argument (already taken by `MaxSteps`)
* Reject delayed value only if already defined in same dataset

* File handling thorugh `AbIn` and `AbOut`
* Atom basis and lattices with many helper functions
* Definition of the reciprocal space
* Occupation of bands and spin types
* Basic relaxation: implemention of `ionmov`, `occopt` with their asscoated variables
* Units of energy and length of Abinit
* (non) SCF calculation
* Partial check for imcompatible definitions and values