Add notification categories and actions

[cri-tech]

I modified the database to have categories on notifications as well as registration for different categories for the user.

I also added the possibility of having actions (for compatible browsers) in the notifications.

Todo :

• improve the entry of actions in the send form

[rwngallego]

Thanks @cri-tech, we will take a look at your PR :)

Maybe @MocioF would you like to see how it works? Looks like cool stuff :)

[MocioF]

I will look at this in this week.

[MocioF]

@rwngallego can you check the docker files? I cannot create a docker image to test this:

Step 3/8 : RUN apt-get install -y vim subversion mariadb-client wget
---> Running in dc0eaedb4caf
Reading package lists...
Building dependency tree...
Reading state information...
E: Unable to locate package vim
E: Unable to locate package subversion
E: Unable to locate package mariadb-client
E: Unable to locate package wget

[rwngallego]

@MocioF please check the latest master, we're now switching to the 5.8 apache docker image.

[MocioF]

@rwngallego Sorry for my delay, but I still have some problems in testing this commit, because I am not able to use the docker image. I'm working on a gentoo machine, so the problem could be I don't have apt installed

[rwngallego]

@MocioF I can extract the changes and rebase our master branch there so that it works with the latest changes. I'll update you when I get some time to do it and probably send a separate PR.

[simohammedhttp]

Hi, are there any updates related to those waited features?
I have a multilingual website with PolyLang, I wonder how to send separate campaigns for each locale?