[XenConcept] Minimum post length 2.3.1

Add:

• added a usergroup permission for bypass the minimum title words

Fixed:

• fixed the permission for bypass the minimum words

Add:

• Added an option to define a regex to restrict the title

Change:

• Rename option Allow only alphanumeric characters to Allow only alphanumeric characters title

Fixed:

• Fix for define a titles more than 150 characters

• Add new option Allow only alphanumeric characters

• Fix error when edit the first post

Add a copyright in the footer. However it is possible to withdraw it for free.