Add dry-run functionality

[egrace479]

Set up to be able to run RollCall for a summary of download and issues that may arise:

• missing or non-unique filenames:
  • For missing filenames, return the data_df.loc[(data_df[filename_col].isna() & (data_df[url_col].notna()))], printed if it's 5 entries or less, otherwise print an error message telling the user where it's saved (see behavior from BuddyCheck for missing images). Remove the -y, so it just prints the error + above behavior.
• duplicate checksums (addresses the "TODO" question),
• summary of where images & downsized images will be downloaded
• logging (see Integrate logging across codebase #64)

[codedbyishika]

Non Interactive Missing File Handling

• Implemented missing file check as non interactive error handing

Duplicate Checksums

• Implemented checks for checking duplicates

Summary

• Implemented summary of where images & downsized images will be downloaded

• Changed main according to new csv handle
• Updated tests to the new features