fixes #358

Problem: Unable to edit files ending with `.html` extension in File Manager

Workaround: For files ending with URL suffix - add `has_url_suffix=1` to $_GET and detect it while editing those files.
fixes #358

Problem: Unable to edit files ending with `.html` extension in File Manager

Workaround: For files ending with URL suffix - add `has_url_suffix=1` to $_GET and detect it while editing those files.
Merge pull request #557 from marekmurawski/issue-358

Fixes #358 - unable to edit '*.html' files in File Manager