Use PHP focus instead of js

[Daniel Besse]

In activity/view page, focus is recomputed in js (as originally implemented). Now the same data is available from the DB (computed with all other metrics). Displaying this one would bring more consistency.

Does it need comparing first?

[Daniel Besse]

focus from PHP and idea of design (displayed for me and jc only currently) (see #136)

→ <<cset 0f93fd1868e4>>

[Daniel Besse]

improved display of focus zones and thresholds from PHP data (see #136)

→ <<cset c75dbdf0a2cb>>

[Daniel Besse]

recomputed focus for all activities and therefore activated new focus display from PHP for all users (fix #136)

→ <<cset ee1e690bde02>>