CSS files are/not included when needed

Problem 1

Description:

When using "CSS mode for syntax highlighting" as "Inline CSS style attributes" the language specific syntax highligh works as expected while "Generic syntax highlighting tags"(e.g: code) are not styled because geshifilter/geshifilter library is included only when "Use CSS classes and an automatically managed external CSS style sheet" is selected.

Solution:

Include geshifilter/geshifilter library for both: Inline "CSS style attributes" and "Use CSS classes and an automatically managed external CSS stylesheet" modes

Problem 2

Description:

Steps to reproduce:
- Select "Use CSS classes and an automatically managed external CSS stylesheet" mode for "CSS mode for syntax highlighting"
Language CSS file is generated and served on pages as expected.
- Select "Inline CSS style attributes" mode for "CSS mode for syntax highlighting";
While the styles are now generated inline the Language CSS file is still included in the markup.

Solution:

Add the Language CSS file only if "Use CSS classes and an automatically managed external CSS stylesheet" mode is selected.