Change log of ansible-backuppc-client role

v3.1.0

Retranscription of work on v3.0.0 of backuppc_server role
Full management of BackupFilesOnly and BackupFilesExclude BackupPC configuration parameters
As announced in v2.0.0, backwards compatibility with v1.X.Y API is no longer assuerd, to leverage code and avoid unexpected behaviours (as happend in v2 for empty include or exclude files lists)
v3.0.0 (and a priori all v3.X.Y) of the role maintains backwards compatibility with v2.X.Y API. But again: can change in fuuture verions. Update your playbooks to the new API asap!
backuppc_scripts desappear, as proposed in defaults/main.yml comments. big refactor of scripts management.
pre and post dump scripts may be individually installed or not and ran with sudo or not
New feature: now it's possible to build pre and post dump scripts from templates. This opens the possibility to develop modules for other apps than MySQL and PostgreSQL

resolution of marginal bug when include or explude files lists are empty, that appears with default variables value's of v1.X.0, that we preserve for backwards compatibility
per and post dumps scripts names and placement parametrisation
simplification ofo some formulas
consistent and extended documentation

Managment of backuppc_rsync_share_names configuration for clients, in order to achieve backups with several rsync
Standardisation of API: all variables are in namespace backuppc_
Backwards variables' compatibility and default values. Can change in future versions, adopt new API!
Some new parameters, previously hard coded
Documentation completion and reorganisation

Change the place of mysql credentials, in order to affect only backuppc user, not root
now accepts mysql without root password defined, as is now the default installation in debian
now the role erases eventual old keys of the backed up host in the known_host of backuppc server

The unix user used by the server to access the client host is now defined as a variable, as well as it's group

Possiblity to configure only the client access to the server, not the host client itself. New variables:
- backuppc_client: boolean, whether to configure the client host or not,
- backuppc_server_home: home directory of user backuppc which is used to perform backups in the server,
Ansible 2.9 compatibility,
Variable name changes: backuppc_db_dump becomes backuppc_db_server_type

First stable version.
configure a host to be backed up by a backuppc server. Configure the client as well as the server,
options to manage:
- pre-dump and post-dump scripts in the client,
- dump of mysql or postgresql databases in these scripts