Cleanup and fixing

[falkTX]

• MOD_BUILD can be used to detect builds of type make moddwarf (hint you can also do make modpush afterwards)
• HAVE_CAIRO is used to check if we should build DGL, skipping it in case it is not available (builds plugins without UI)
• Some little details on html/js were incorrect
• 1st factory preset was empty
• windows builds only need to check for _WIN32 which is always present, no need to use any other macros
• mod builds assumed /data/user-files/ dir, which is not true if running as part of mod-app