minor changed to the new KOI planets.
Added error bars to KOI-200.xml. Source:
http://arxiv.org/pdf/1304.6002.pdf
Updated cleanup script to automatically convert 'error' attributes to 'errorplus' and 'errorminus' attributes.
Modified cleanup script so that it does not delete empty tags which have
attributes.
Merge commit '791787a9bc5bf723d8647f18287efe361d41c7c8' into develop
fixed planet errors according to the established standard, removed logg and fixed transititime position

- a new standard was decided for adding errors, see (https://github.com/ryanvarley/open_exoplanet_catalogue_advanced/issues/2) for the discussion
- transittime sometimes was tagged in the star not the planet
- logg has been removed as it can be calculated from R and M
added transittime and rossitermclauglin to valid tags in cleanup.python