user manual: add instructions to build latest sources on Mac OS X
user manual: update and rename section "Specific installation examples"
user manual: remove obsolete text, refactor

Remove unnecessary sections of chapter 2, because the topics are covered
in step-by-step instructions:
- Prerequisites
- Compiling

Move section "Step-by-step building instructions" into own file.
user manual: merge all advanced info on CMake usage into a single node