Low vs. high res option for occurrence

[jmcalabrese]

@xhdong-umd Can we repurpose the code that gives the user the choice between a shared or individual grids for home range analysis to offer a choice between low and high res for occurrence estimation?

I think the current ctmm default res settings for occurrence are sufficient for the "high" option, while the "low" option should be chosen to yield a substantial speed-up without degrading the estimate too much.

I think the popup box should read:

Estimate Occurrence Distribution

• Low resolution (for exploratory analysis)
• High resolution (for publication-quality analysis)

I think low res should be the default. We may also want to display a warning message in red on the occurrence page if the estimate is low res to remind the user that the estimate is not production quality.