Test suite: Add test_section class
RPM file list test: Use new test_section class
SQL schema: Introduce table symboldb.file_attribute

This collects the file attributes which are constant across
RPM rebuilds.  They are no longer stored in symboldb.file_contents
(where they do not belong because they are metadata).
cxxll::rpm_file_info::capabilities: New member
cxxll::rpm_parser_state: Extract file capabilities
SQL schema: Add column caps to table symboldb.file_attribute
RPM load test: Add rsh package for testing file capabilities