Added support for ini-file.

Added _meta dictionary with hostvars in --list json output.

contrib/inventory/spacewalk.ini

+# Put this ini-file in the same directory as spacewalk.py
+# Command line options have precedence over options defined in here.
+
+[spacewalk]
+# To limit the script on one organization in spacewalk, uncomment org_number
+# and fill in the organization ID:
+# org_number=2
+
+# To prefix the group names with the organization ID set prefix_org_name=true.
+# This is convenient when org_number is not set and you have the same group names
+# in multiple organizations within spacewalk
+# The prefix is "org_number-"
+prefix_org_name=false
+
+# Default cache_age for files created with spacewalk-report is 300sec. 
+cache_age=300