epiphany and baobab user help

[Ekaterina Gerasimova <kittykat3756 gmail com>]

Hi, epiphany (Web) and baobab (Disk Usage Analyzer) have new user help which is relatively finished for 3.10 and it is quite short.

The only changes that I foresee which could happen before the 3.10 release are:

* typo fixes

* epiphany may have some new pages added

* baobab may have some new functionality added that may require a few paragraphs to be changed, but I think this is not going to happen in time for 3.10