autocomplete: dictionary

Remove duplcate words in the disctionary.
autocomplete: tests added for duplicate words
Autocomplete: use of a set

It fits more with what we want.
Merge pull request #1 from l-vincent-l/NAVITIAII-844

Use of a std::set
Merge pull request #343 from kadhikari/NAVITIAII-844

Navitiaii 844