Missing HomographyMethodRHO HomographyMethod added

[Krzysztofz01]

Hello!
This is my first pull-request here. There is a link to the official OpenCV documentation attached to the FindHomography function. It mentions four supported homogpraphy methods, but in gocv only three of them have been implemented. I ran local tests on whether the library can work with the RHO method, and all the tests were successful. In accordance with the documentation, I propose to add the missing method.

I also noticed an inconsistency in the names of values and the type (HomographyMethod/HomograpyMethod), but I assume that due to compatibility with previous versions of the library, it will be hard to correct this (marking old values as deprecated and adding new ones without a typo?).

Greetings

[deadprogram]

Thanks for the addition @Krzysztofz01

As far as the misspelling, I think it should be fixed. Once GoCV hits a 1.0 release then we will respect the usual Go version guarantees.

If you want to make that change in this same PR, that would be fine with me! :)

[Krzysztofz01]

I have corrected the typos mentioned earlier. I think the changes are ready to be merged :)

[deadprogram]

Thanks for adding this @Krzysztofz01 now merging.