Added support for PHP profiling

On hosting added ability to profiling PHP with Tideways XHProf Extension.

The profiler allows you to identify bottlenecks in the code for their further optimization.

With it, you can find out:
- What functions and how many times were called during request processing.
- How long each function was running.
- How much RAM was used by the function and peak consumption values.

Work with the profiler is performed through the section "Hosting → My sites → PHP profiling».

To get a report, it is enough:
1. Enable profiler.
2. Add your IP or developer's address to the list.
3. Perform actions for which you need to collect information from the added IP on the site.

Detailed information can be found in our wiki.