feat: creation of new generic function so save XcmsExperiment object

[philouail]

Hi so this is just a draft, but I thought it might be easier to discuss here. I might need a bit of back and forth as it's the first time I do that :) Hope it's fine for you to do it like that. I'll also leave it as draft to avoid confusion.

See my comments for the parts that I'm confused about !

[philouail]

Oh and also I tried to do the necessary changes in description and NEWS files, but can you check if it looks OK ? Maybe there's different rules for XCMS compared to the other packages I contributed.
And I have to look into this NAMESPACE thing, to see how to do it manually tomorrow.

[jorainer]

For the NAMESPACE, just add

export RDataParam
exportMethods storeResults

that should be enough. Description and NEWS are OK - yes, there is a different format here, but what you added is fine.

[philouail]

Hi @sneumann so this PR is related to #693, it establish a new generics function storeResults that will allow to save xcms results objects into different format. This PR also implement the first format which is .RData with the RDataParam.
I will then look into the Plain text file format and lastly MzTab-m they will each have they own param class and specific method.

Tell me if there is anything unclear or I need to change something.

[jorainer]

Thanks Phili! I'm fine with this PR.

Please @sneumann also have a look whether you're OK with the general approach we take here.

Only thing, @philouail , please address the one point regarding the dll file.

[sneumann]

Hi, looks good to me, thanks for the nice work !
Yours, Steffen

[sneumann]

Cool, so ready to merge from my side.