SuReal: `lg-get-dict-entry` scheme primitive

* added a `lg-get-dict-entry` scheme primitive for constructing an entry for a word
    - usage: `(lg-get-dict-entry (WordNode "yes"))`
    - for upcoming SuReal usage
    - the atom types and atomic formula are extracted from the viterbi code
    - the `ReferenceNode` thing added by me awhile back is not really needed due to later changes, so removed in the same commit while I am editing that file

* slightly updated viterbi code
    - made it uses the LGDictReader
    - made it build-able, and the corresponding tests passing
    - kept it commented out in the CMake file

The LGDictModule perhaps should be on another directory... maybe move it when the language learning part is implemented.