Modify SP to handle elevation information

THIS REQUIRES THAT THE "elevation" COLUMN BE ADDED TO ag_login TABLE
Update metadata dump to retrieve elevation
Add elevation retrieval
Separate geocoding update code from retrieval code
Add link to update geocoding info on wwwadmin
Modify geocoding functions

- Add more detailed error messages to lat/long and elevation lookup functions
- Add a limit parameter and a retry flag
Add basic statistics to geocoding page on wwwadmin
Add python script-level headers
Change tabs to spaces
Add docstring; change Exception clause
Merge pull request #572 from adamrp/elevation2

Elevation2
Merge branch 'master' of git://github.com/qiime/qiime_web_app