Bug 15492: New sysprefs and permissions

Bug 15492: New sysprefs and permissions

In order to make this module unrelated to the SCO module, this
patch introduces the following sysprefs:

- SelfCheckInMainUserBlock
- SelfCheckInModuleUserID
- SelfCheckInTimeout
- SelfCheckInUserCSS
- SelfCheckInUserJS

It also adds a new user flag and sub-permission:

- self_check => self_checkin_module

and moves the circulate => self_checkout permission into

- self_check => self_checkout_module

Descriptions are adjusted accordingly.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>