Purpose is to ease their ordering and understanding.

Main idea of this commit is to simplify the various options of
ir.actions.server model. Purpose is to make it a simple tool to
execute some actions or python code. This has two main consequences

 * create and update server actions are simplified to update only the
   current record. Complex options can always be achieved by python code
   instead of error-prone option building mechanism;
 * condition of server actions is removed. If a condition is necessary it
   can either be included in a code server action, or integrated in an
   automated action;

This commit features :

 * remove 'client_action' server action type. Indeed this can be achieved
   with a code server action returning an action;
 * remove 'condition' on ir_actions_server model. From now on conditions
   and triggers are managed in server action code or using automated
   or scheduled action;
 * clean 'create and copy a record'. Create and link are the proposed
   options. Copy of the record or of a selected record is removed. Link
   is simplified by removing the parsed expression that allowed complex
   path update. It is simpler to write code than write python-like
   expression in char fields;
 * remove 'use_write' options. It now simply updates a record;
 * remove 'write_expression' as it is replaced by code actions;
 * remove 'ref_object' not used anymore with the removal of "choose
   a record";
 * remove helper to build an expression not used anymore with the removal
   of "write expression";
 * remove object ID finder;
 * removed template display when choosing an email template; just go
   on the template if you want more details;
 * refactor server action form view to reflect changes. It will be used
   in future commits as base view for automated and scheduled actions;
 * add 'sequence' in list view;
 * add new 'usage' selection field allowing to distinguish which model
   uses the server action. Indeed as server action will soon be used
   in scheduled or automated actions having a clue about the usage
   is always helpful;

Thanks to @fpodoo for the original idea and preliminary work. Thanks to
@jpr-odoo for first developments. Thanks to @jem-odoo and @rco-odoo
for reviewing.

Use record / records instead of deprecated locals

There is a traceback when we are trying to install module from the list
view and clicking on the button 'Module Immediate Install'.
This traceback appears because of a server action that has not been migrated
during the rev https://github.com/odoo/odoo/commit/d465346f1

To fix this, we've converted the server action in new API.