Remove unnecessary functions

[keflavich]

Remove unimplemented/unused code:

• [ ] https://github.com/radio-astro-tools/uvcombine/blob/3bb3f674977c262709a0593ad468c13c5daa2f2e/uvcombine/uvcombine.py#L177
• [ ] https://github.com/radio-astro-tools/uvcombine/blob/3bb3f674977c262709a0593ad468c13c5daa2f2e/uvcombine/uvcombine.py#L256
• [ ] https://github.com/radio-astro-tools/uvcombine/blob/3bb3f674977c262709a0593ad468c13c5daa2f2e/uvcombine/uvcombine.py#L281
• [ ] https://github.com/radio-astro-tools/uvcombine/blob/3bb3f674977c262709a0593ad468c13c5daa2f2e/uvcombine/uvcombine.py#L444
• [ ] https://github.com/radio-astro-tools/uvcombine/blob/3bb3f674977c262709a0593ad468c13c5daa2f2e/uvcombine/uvcombine.py#L460
• [ ] https://github.com/radio-astro-tools/uvcombine/blob/3bb3f674977c262709a0593ad468c13c5daa2f2e/uvcombine/uvcombine.py#L476
• [ ] https://github.com/radio-astro-tools/uvcombine/blob/3bb3f674977c262709a0593ad468c13c5daa2f2e/uvcombine/uvcombine.py#L494
• [ ] https://github.com/radio-astro-tools/uvcombine/blob/3bb3f674977c262709a0593ad468c13c5daa2f2e/uvcombine/uvcombine.py#L512
• [ ] https://github.com/radio-astro-tools/uvcombine/blob/3bb3f674977c262709a0593ad468c13c5daa2f2e/uvcombine/uvcombine.py#L535
• [ ] https://github.com/radio-astro-tools/uvcombine/blob/3bb3f674977c262709a0593ad468c13c5daa2f2e/uvcombine/uvcombine.py#L607

[e-koch]

All of these should have been removed or deprecated in #28