Calculate further informations about the nutritional plan

Refs #56
Show detailed nutrition data for each ingredient

--HG--
extra : amend_source : 7ef209cabb621eff074e4322710f099e126585f3
Use a default quantization when calculating nutritional data

--HG--
extra : amend_source : 857e0f70ce36bb7943cf4778802df090866acaf2
Add tests for the percent and the per_kg nutritional calculations
Show table with nutritional information on PDF as well
Don't test with python 2.6 anymore

Among other things, this simplifies the handling of decimals, since it's
not necessary to first convert to string.
Update mobile template for nutritional plan
Make the clean method for ingredients more robust
Perform further validations for numeric fields, fixes #57
Merge