Improve GreaterThan constraint

[pvk-developer]

Problem Description

Allow the user to pass a certain value to the GreaterThan constraint instead of just columns. Also allow the possibility to choose when using transform strategy, which value to keep (the lower or the higher).

Expected behavior

from sdv.constraints import GreaterThan

gt_int_column = GreaterThan(low=1, high='column', handling_strategy='transform', transform_value='high')
gt_column_int = GreaterThan(low='column_a', high=100, handling_strategy='transform', transform_value='low')
gt_columns = GreaterThan(low='column_a', high='column_b', handling_strategy='transform', transform_value='low')

[npatki]

Is it better to add static values to this constraint, or to create other constraint(s) for this? See discussion in #409