Bug fixes in caching and comparison of Wyckoff positions

[bfield1]

Fixes for issues https://github.com/gap-packages/cryst/issues/42 and https://github.com/gap-packages/cryst/issues/44 . Tests for the fixes.

In testing, I came across another bug, where comparison of certain LeftAction WyckoffPositions (with complicated conjugations) would raise errors about rationals being where integers were expected. I traced this down to ImageAffineSubspaceLattice not handling the case of left-acting affine matrices (instead treating them as if they were right-acting).

[codecov[bot]]

Codecov Report

Merging #45 (f7f55bf) into master (fbf54fb) will increase coverage by 0.00%. Report is 2 commits behind head on master. The diff coverage is 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #45 +/- ## ======================================= Coverage 94.32% 94.32% ======================================= Files 24 24 Lines 7572 7582 +10 ======================================= + Hits 7142 7152 +10 Misses 430 430 ``` | [Files](https://app.codecov.io/gh/gap-packages/cryst/pull/45?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=gap-packages) | Coverage Δ | | |---|---|---| | [gap/cryst.gi](https://app.codecov.io/gh/gap-packages/cryst/pull/45?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=gap-packages#diff-Z2FwL2NyeXN0Lmdp) | `85.77% <100.00%> (+0.12%)` | :arrow_up: | | [gap/wyckoff.gi](https://app.codecov.io/gh/gap-packages/cryst/pull/45?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=gap-packages#diff-Z2FwL3d5Y2tvZmYuZ2k=) | `87.78% <100.00%> (+0.17%)` | :arrow_up: | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/gap-packages/cryst/pull/45/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=gap-packages)