Merge branch 'issue/filesystem-path-comparison' into 'master'

Add missing const to path operator==

See merge request amdis/amdis!227

amdis/common/Filesystem.hpp

@@ -90,7 +90,7 @@ namespace AMDiS
       bool is_directory() const;
 
       /// Lexicographically compares two paths
-      bool operator==(path const& p)
+      bool operator==(path const& p) const
       {
         return this->string() == p.string();
       }