This changed very much in Odoo 11. To get an idea how to create Configuration pages in Odoo 11, my tip is to look for files named res_config_settings.py and res_config_settings.xml.

Here is a short example of a configuration in Odoo 11:

Example model

class Session(models.Model):
    _name = 'openacademy.session'

    name = fields.Char(required=True)
    seats = fields.Integer(string="Number of seats")

The field 'seats' will get a default value configurable in the configuration that we will create. In odoo 11 all configuration is done in the same model, which we will extend via _inherit.

Configuration model res_config_settings.py

class ResConfigSettings(models.TransientModel):
    _inherit = 'res.config.settings'

   default_seats = fields.Integer(default_model='openacademy.session')
    my_setting = fields.Char(string='My Setting')

    def get_values(self):
        res = super(ResConfigSettings, self).get_values()
        res.update(
            my_setting=self.env['ir.config_parameter'].sudo().get_param('openacademy.my_setting')
        )
        return res

    def set_values(self):
        super(ResConfigSettings, self).set_values()
        self.env['ir.config_parameter'].sudo().set_param('openacademy.my_setting', self.my_setting)

Fields with the prefix 'default_' will be handled automatically by Odoo
to provide default values for fields in some models.
Other configuration values need to be handled manually in get_values and set_values.

Finally there is the view for this model. It is quite a lot code,
to match the same style of the other Odoo config pages.

<?xml version="1.0" encoding="UTF-8"?>
<odoo>
    <record id="openacademy_settings_view2" model="ir.ui.view">
        <field name="name">Openacademy Configuration</field>
        <field name="model">res.config.settings</field>
        <field name="inherit_id" ref="base.res_config_settings_view_form" />
        <field name="arch" type="xml">
            <xpath expr="//div[hasclass('settings')]" position="inside">
                <div class="app_settings_block" data-string="Open Academy Data-String" string="Open Academy" data-key="openacademy">
                    <h2>General Settings</h2>
                    <div class="row mt16 o_settings_container">
                        <div class="col-xs-12 col-md-6 o_setting_box">
                            <div class="o_setting_right_pane">
                                <label for="my_setting"/>
                                <div class="text-muted">
                                    Description text 1
                                </div>
                                <div class="content-group">
                                    <div class="mt16">
                                        <field name="my_setting" class="o_light_label"/>
                                    </div>
                                </div>
                            </div>
                        </div>
                        <div class="col-xs-12 col-md-6 o_setting_box">
                            <div class="o_setting_right_pane">
                                <label for="default_seats"/>
                                <div class="text-muted">
                                    Description text 2
                                </div>
                                <div class="content-group">
                                    <div class="mt16">
                                        <field name="default_seats" class="o_light_label"/>
                                    </div>
                                </div>
                            </div>
                        </div>
                    </div>
                </div>
            </xpath>
        </field>
    </record>

    <record id="openacademy_settings_action" model="ir.actions.act_window">
        <field name="name">Openacademy Configuration</field>
        <field name="res_model">res.config.settings</field>
        <field name="view_id" ref="openacademy_settings_view2"/>
        <field name="view_mode">form</field>
        <field name="target">inline</field>
        <field name="context">{'module' : 'openacademy'}</field>
    </record>

    <menuitem id="openacademy_settings_menu" name="Configuration"
              parent="main_openacademy_menu" action="openacademy_settings_action"/>
</odoo>