Feature/issue51 rearrange readme structure (#65)

* added images with predefined size, extended TOC

* Update readme.md - metrics naming description

changed TOC structure, added naming conventrion, basic table structure for domian, subdomain, units description.

* Additional info form untis description

* Rearraged header, added several TOC refs

* added back to toc links

* Descr for domains + subdomains table

* Added description to every section

* Renamed several headers

* Updated TOC

* Sub, Pub metrics links updated

* Updated TOC

* Added links from PCF metrics table to mapping.

* Change cpu platform metrics header

Author: sberdyshev