Add contextual searching / filtering for mass correction

[matgille]

Is your feature request related to a problem? Please describe.
When mass-correcting, we can't filter the entries nor select some entries with context filtering. Example: in spanish, "la" can be a pronoun or a determinant: followed by a noun, it is a determinant.

Describe the solution you'd like
I don't know if a contextual search feature would be really useful in the main search function, but it would fasten the mass corrections.
In the "similar" function, I would filter the result selecting all "la" tokens followed by a noun, and then change the Pos and morph for all of the filtered tokens, instead of having to check the entries one by one.

[PonteIneptique]

I think this is connected to #200 to some extent and I also think we can do something about it, but not a perfect thing. We should probably limit the distance (5 ?) and have a SQL join which checks a second filter on (n_order <= current.n_order -+ 5)

I'd like the POV of @MrGecko on this one.