Category Block Page feature - new in v5.6

Allows a different block template for a category or list of categories.

A different message or guidance can be given to user depending on 
 block category.

All files in this directory with the suffix .html are considered templates.

They are processed in alphabetical order.

Each template is in the same format as the standard template.html (in the 
 language directory) with the addition of a first line added:-

#category: "category_name"
or
#category: "category1,category2,..."

Filter Blocks that have a main category which matches category_name will have 
 block page formated from this template.

If a category is also in a later template file then the later one wins.

If a category is not in any of the template files then the standard template 
 will be used.  

The location of this directory is defined in the e2guardianfn.conf file by
 the 'htmltemplatedir' setting.
So if different templates are required for a filter group then a similar 
 directory can be setup within the filtergroup's list directory and the 
 'htmltemplatedir' setting adjusted accordingly.

PIP 12 July 2023
