No alt lang strings

Adding lang string for images with no alt tag
Refactoring code and content load change

Refactoring code to get more readable library. Changing principle of
programming logics. Loading content and removing images first, then
breaking into smaller parts and outputting.
Lib file editing to work with DOMDocument

Lib file is edited to work with DOMDocument. New function takes chapter
and changes all image tags to p tag with content of an alt attribute of
an image file. Output length is handled after removing images. Also
function is used for encoding conversion (Croatian characters).
Minor change in if condition
Merge branch 'dev'