Tokens - simplify and standardize interface of search methods
minor #547 Tokens - simplify and standardize interface of search methods (keradus)

This PR was squashed before being merged into the 1.0.x-dev branch (closes #547).

Discussion
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Tokens - simplify and standardize interface of search methods

Some methods in `Tokens` return `Token` that we are searching for and it's index by last parameter passed by reference.
But we often need only that index, no `Token` itself.
And other methods return only index.

So let it be one way - return index, and if we need `Token` then grab it by index.

Commits
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e0ab752 Tokens - simplify and standardize interface of search methods