Ninst

- make dev_setup return list of arches (12)
- add `RSZ_PSF_KRNL` (12)

- fix `install_tool` (11)
- slight optimisations

- add `install_tools.urlopen_cached` (10)
- add `install_tools.extractall` (10)
- remove `resources.get_refimg`
- misc tidy

- `install_tools.askdirectory`: suppress prompt when `name` found in env (9 <- NiftyPET/NIPET17)
- misc build/test framework updates
- minor installation doc update

- enhance `check_depends()` (8)
- arbitrary binaries
- auto-parse version tuple
- documentation updates
- add py3.9
- tests: more succinct traceback

- add `cmake_cuda` (7)