Update import tab "Option C: Upload dataset"

[cristinamullin]

Is your feature request related to a problem? Please describe.

A shiny app user may want to upload their own data using "Option C: Upload dataset" on the import tab. This option is not fully fleshed out and needs to be updated and tested with example datasets.

When a dataset is uploaded, we need to check that all TADA required columns are included in dataset and we need to run autoclean on the dataset on import. On import, at least the following two functions should be run:

1. TADA_CheckRequiredFields()
2. TADA_AutoClean()

Note: The package function TADA_CheckRequiredFields may need edits to best meet this use case.