LayeredInclude: added missing doc
renamed auto_read test to backend_mgr test
BackendMgr: refactored. Die if obsolete read_config_dir is specified
dist.ini: added dep on Module::Runtime to avoid test failure on Mac and Windows
BackendMgr: fixed trace and error message that referred to old auto_read
BackendMgr: write_config_dir parameter now triggers a die
BackendMgr: added default_layer backend parameter
removed comment
BackendMgr: added $home override for tests
BackendAny: lack of suffix method is now an info not a warning
CheckList: added clear_layered method
BackendMgr: added traces
BackendMgr: removed mentions of Augeas
CheckList: removed duplicated (!) attribute
CheckList: Added clear_item method
CheckList: clear now reset (undefs) a check-list instead of setting items to 0

This enables layered values to show through
CheckList: added user mode to retrieve data
get_check_list_as_hash: added user mode, don't return 0 for undef items
set_checked_list: avoid clear and set. Now just sets what's needed
set_checked_list_as_hash: Missing items in the given list of parameters are now reset