Create query profiler

[marco-scoppetta]

Problem to Solve

It is currently not possible to know how many rules have been analysed and used for a given query. Also there is no way to know how many nodes and edges have been traversed during a query execution.

Current Workaround

N/A

Proposed Solution

Create a QueryProfiler that collects data about every executed query:

1. how many nodes(how many reads, may be differentiate cached and not cached) it touched during an execution
2. how many inference rules it checked (if by execution it needed to recheck rules, they should be added to count)
3. how many inference rules it executed

The collected statistics should be returned together with map and explanation in the Answer. The profiler should be used only when a specific flag is enabled (as it will probably impact on performance)