Add DisableElmishSyntax setting

[nojaf]

Initial attempt to solve #1198
Left to do:

• Add tests that cover all Elmish expression cases
• Write documentation

[knocte]

Another contra I see here is that the fsharp_max_elmish_width should have no effect when fsharp_disable_elmish=true.
This again might be just a tad confusing for end-users.

Then how about renaming fsharp_max_elmish_width to fsharp_max_elmish_width_if_enabled?

[nojaf]

Renaming a setting and not introducing a breaking change is though combination, not something I want at this moment.
Perhaps for the next major release (of which I have no intentions at the time of writing) but then again I don't think it adds that much value.

[knocte]

Understand, I was suggesting something for having less confused users.