Adds variable to control maximum subject length

Creates variable 'cgce_Kayako_displayMaximumSubjectLength'
in .install file and adds option to edit the variable
under the 'CGCE > Kayako Link > Display Settings' admin menu.
Adds optional 'maxlength' variable to textfields
Adds 'maxlength' attribute to Support Center subject
Version 7.x-1-1.2

Updates info and Changelog files to reflect Maxlength merge.