Remove Drizzle Kernels: gaussian, lanczos, and tophat

[stscijgbot-hstdp]

Issue HLA-1216 was created on JIRA by Steve Goldman:

It was found that several kernels that are available options in drizzlepac do not conserve flux and should be removed as options. This change is related to recent changes in the standalone drizzle package and Jira ticket AL-774.

 

The kernels that should be removed are gaussian, lanczos, and tophat. What should remain is point, square, and turbo. 

 

The documentation as well as drizzle unit test also need to be updated. 

[stscijgbot-hstdp]

Comment by Steve Goldman on JIRA:

A note from mihai:

I know that people use those kernels. Tophat simply does not work correctly (and likely it never did before) and it will not be fixed. It has to go.
However, technically the others are OK in the sense they don't produce outrageous results. For the very least it should be documented and/or software should issue a warning about flux not being conserved ```
After discussions with folks on the drizzle_updates slack channel, it was decided that I will add warnings for “lanczos” and “gaussian” that we cannot guarantee that they are conserving flux, but leave them as options.

I also removed “tophat” as an option.  

[stscijgbot-hstdp]

Comment by Steve Goldman on JIRA:

Closed by PR-1786