Asilib

Added
- `asilib.Imagers()` class to make mosaics and synchronize plotting multiple imagers. The first two methods implemented are:
- `asilib.Imagers.plot_fisheye()` to plot fisheye lens images from multiple imagers, and
- `asilib.Imagers.plot_map()` to project images from multiple imagers onto a map. This method has an `overlap` kwarg that by default masks out the (lat, lon) skymaps that map to pixels that overlap with a neighboring imager. This is a surprisingly efficient method that needs to be run just once (tested for up to five imagers; I'm unsure how a 10 or a 20 imager array will fare).
- Added plot tests for the two `Imagers` methods.
- Added an `Imagers()` description in the Get Started and API pages.
Changed
- Refactored the Donovan+2008 auroral arc example to use `asilib.Imagers.plot_map()`.
- Added a check to allow custom `matplotlib.colors.Normalization` object to be passed for `color_norm`.

Added
- Support for RGB images in `asilib.Imager.keogram()`.

Changed
- Simplified `asilib.Imager.__getitem__()` to repay the technical debt. Before the method was difficult to reason about and it processed the [time] and [start_time:end_time] slice cases separately. Now `__getitem__` handles both of those cases in the same way.
- Simplified how the `Imager._keogram` array is allocated when `asilib.Imager.keogram()` is called.
- Edited the Imager flowchart.

Added
- Deprecation warnings to the legacy asilib plotting functions and in the API reference. They will be removed in or after December 2023.

Changed
- Fixed the `color_norm` keyword argument in `asilib.Imager()` methods. Now it defaults to `None` so the normalization is correctly overridden. Also, the `color_norm` docstring is updated to clarify the hierarchy.
- Changed the `data` to `file_info` argument in `asilib.Imager()`, and all ASI loaders, to more clearly convey the purpose of the variable.

Added
- A tutorial using `asilib.Imager()`.
- Documentation in contribute.rst describing the `asilib.Imager()` interface. Simplified the `asilib.Imager().__init__()` docstring and point to the thorough interface description in the new Contribute section.

Changed
- Refactored how `asilib.Imager()` deals with single- and multi-image instances. Now, each ASI `wrapper` function does not need to load a single image if `time` is specified, `asilib.Imager()` does this instead.
- Refactored the `themis`, `rego`, `trex_nir`, `lamp_phantom`, and `psa_emccd` wrapper functions with the new `asilib.Imager()` interface.
- Due to this change, the `asilib.Imager.__getitem__()` method significantly simplified.

Added
- Refactored all examples from `examples/v0/` and saved them in `examples/v1/`.
- Added the v1 examples to the Examples documentation tab. During the v0->v1 transition, users can see the examples in both the v0 and v1 interfaces.
- Removed experimental warning from Imager API Reference and moved it to the Legacy API Reference.