rename importers to standardize "import" terminology

[thpralas]

rename following importers :

• loadFromBiom --> importBIOM

• loadFromQIIME2 --> importQIIME2

• readQZA --> importQZA

• loadfromMothur --> importMothur

• loadFromMetaphlan --> importMetaphlan

• loadFromHumann --> importHumann

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 43.90244% with 46 lines in your changes are missing coverage. Please review.

:exclamation: No coverage uploaded for pull request base (devel@1d01162). Click here to learn what that means.

:exclamation: Current head b91e221 differs from pull request most recent head a9e0921. Consider uploading reports for the commit a9e0921 to get more accurate results

Files	Patch %	Lines
R/deprecate.R	0.00%	18 Missing :warning:
R/importMetaphlan.R	0.00%	10 Missing :warning:
R/importHumann.R	25.00%	6 Missing :warning:
R/importMothur.R	76.92%	6 Missing :warning:
R/importQIIME2.R	45.45%	6 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## devel #505 +/- ## ======================================== Coverage ? 72.82% ======================================== Files ? 40 Lines ? 4648 Branches ? 0 ======================================== Hits ? 3385 Misses ? 1263 Partials ? 0 ```

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[antagomir]

Ok to me when the above points are resolved.