Fixed the bugs cuasing interval to be defined as none. This required changes...

Fixed the bugs causing interval to be defined as none. This required changes to the FDSNFactory.py after fixing this another bug was found in IAGAWriter2002.py, this was also fixed by changing the variable type for the value elevation. The change made to the test_metadate.py script was something that Nich told me about that hasnt been merged in yet. Happy to take it out if need be but I left it in for the time being.