cxxll::pg_private::dispatch<*>::load(): Improve error message
cxxll::pg_private: Move exception throwing out of templates

This avoids duplication and should reduce code size.
symboldb_rpm_load: Do not truncate contents for interesting files

These files are in /etc or register services.
cxxll::pg_private: Another more detailed error message
database::update_contents_preview(): Remove bogus assert
symboldb_rpm_load: Keep file contents based on more paths