Beta version of ss-engine

• This version includes all of the required functionalities of semantic search in Mattermost.
• This version uses Mattermost cookies to authenticate users on the backend.

Note that Mattermost doesn't just send cookies to any domain. The search engine should be deployed on the same domain as the Mattermost server for it to work properly.

Pre-release

Merge pull request #3 from iCog-Labs-Dev/decoupling-api

Decoupling api