framework: Add "init_args" function to Plugin
    
    Add "init_args" function to "Plugin" class which is executed
    after reloading plugins in sealert (get_plugins). This allows
    for changing "fixable" and "report_bug" variables after plugin
    analysis (plugins are reloaded and "analyse" is not executed
    again, therefore it's necessary to set the variables elsewhere).
    
    Signed-off-by: Vit Mojzis <vmojzis@redhat.com>