convert trig datetime transform to standalone

[thomasarmstrong98]

Pull Request

Description

First PR so let me know what if I've missed any steps etc!

Changed the cosine/sine decomposition of datetime values to standalone function now, so it can be used without the tiling. In addition added the minutes/60 to the daily decomposition for more granularity - this can be reverted as to not alter the _create_time_image function from original.

Fixes #

How Has This Been Tested?

Tested the old _create_time_image with new (with no minutes added) which matched.

• [X] Yes

Checklist:

• [X ] My code follows OCF's coding style guidelines
• [X] I have performed a self-review of my own code
• [X] I have made corresponding changes to the documentation
• [X] I have added tests that prove my fix is effective or that my feature works
• [X] I have checked my code and corrected any misspellings