[ENH] Compare two (and only two) dataframes by common attributes

[hadarsharon]

Is your feature request related to a problem? Please describe.
For starters, compare two dataframes (not more at this stage) by common attributes which are shared across dataframes and can be accessed without casting, joins or transformations.
This should be the simplest comparison both in terms of implementation and compatibility.

Describe the solution you'd like
Left and Right dataframes should be possible to compare by common attributes, namely:

• Number of rows
• Number of columns
• Order of columns
• Datatypes