Very first draft for XML schema definition file.
Changes proposed by hanno
if no value is set, no errors can be set

Now, there are nor errorminus, errorplus, if no value is submitted
corrected error bars for temperature stated in http://arxiv.org/pdf/1401.6811v1.pdf
Corrected DE Format
Removed error bars with value 0
Current version

Only 2 of 1092 xml files are recognized with a not accepted format
Added KOI-1257 Binary system. Source: http://arxiv.org/abs/1406.6172
Added WASP-117b. Source: http://arxiv.org/pdf/1406.6942v1.pdf
fixed tag name.
typos
Added python 3 snippet
Added XO-2S. Source: http://arxiv.org/abs/1407.0251
closes #283
Added number format check to cleanup script
Fixed number formating
fixed format in attributes
additional error checking
Added support for positive numbers in scientific format regex
Fixed formatting errors.
Two planets retracted in Gliese 581. Source:
http://www.sciencemag.org/content/early/2014/07/02/science.1253253.abstract