Performance issues when synchronizing with Docker containers

[boris-brtan]

Hi, as I promised here i gather some information and created an example for our project with mutagen syncing.
I written the basics into this shopsys/shopsys#1051.
The main problem is that mutagen consumes CPU also using native watcher.
And it is 0.5x - 3x slower than unison for now but i look forward for new versions and will update this issue with new data.