SOC-4118: Slowness in suggestion portlet (social part)

Fix description:
- The idea is to first limit the total amount of provided suggestions and also get the suggestions only from a sample.
It will take a random sample of my connections and for each of the selected connections it will analyze only a sample
of their connections such that we will always have a limited amount of connections to treat which allows to get a result faster
even if I have a lot of connections or my connections have a lot of connections.
- Implemented getLastIdentities and getLastSpaces