Added excel normalization code and associated tests

[IamEzio]

Fixes #2994

Related to #3027

This PR adds excel normalization code, that is, removes null rows and columns when reading the excel files.

Screenshots

excel-norm.mp4

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[IamEzio]

@dmos62 PTAL. Thanks!

[Anish9901]

Looks good overall, just a minor suggested change.

[Anish9901]

I think there should be a conderation here for whether or not the first row of the data is a header in #3030.

[IamEzio]

Yeah, that is planned for the coming PRs.

[dmos62]

Edited top post to have this close #2994. There might be follow up PRs that will touch up on the feature, as outlined in #3027, but those file types will be moderately accepted by the time this PR is merged.

[Anish9901]

Okay, this looks good to me, thanks for your work on this @IamEzio!