Fixed AnnData import/export, multiple inputs, combineSCE

[mingl1997]

Added: AnnData import and export Multiple object processing with separate/combined workflows

Updated: SCE to AnnData conversion Vignettes and function documentation

Fixed: CombineSCE errors

[codecov[bot]]

Codecov Report

Patch coverage: 9.78% and project coverage change: -0.65 :warning:

Comparison is base (c35f26a) 53.83% compared to head (54312f6) 53.18%.

:exclamation: Current head 54312f6 differs from pull request most recent head 364e7b1. Consider uploading reports for the commit 364e7b1 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## devel #703 +/- ## ========================================== - Coverage 53.83% 53.18% -0.65% ========================================== Files 78 79 +1 Lines 12422 12579 +157 ========================================== + Hits 6687 6690 +3 - Misses 5735 5889 +154 ``` | [Impacted Files](https://app.codecov.io/gh/compbiomed/singleCellTK/pull/703?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=compbiomed) | Coverage Δ | | |---|---|---| | [R/runQCUtils.R](https://app.codecov.io/gh/compbiomed/singleCellTK/pull/703?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=compbiomed#diff-Ui9ydW5RQ1V0aWxzLlI=) | `0.00% <0.00%> (ø)` | | | [R/sctkQCUtils.R](https://app.codecov.io/gh/compbiomed/singleCellTK/pull/703?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=compbiomed#diff-Ui9zY3RrUUNVdGlscy5S) | `0.00% <0.00%> (ø)` | | | [R/importCellRanger.R](https://app.codecov.io/gh/compbiomed/singleCellTK/pull/703?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=compbiomed#diff-Ui9pbXBvcnRDZWxsUmFuZ2VyLlI=) | `42.94% <25.00%> (ø)` | | | [R/combineSCE.R](https://app.codecov.io/gh/compbiomed/singleCellTK/pull/703?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=compbiomed#diff-Ui9jb21iaW5lU0NFLlI=) | `71.95% <62.96%> (-1.77%)` | :arrow_down: |

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.