Rename some templates in the nutrition app

--HG--
rename : wger/nutrition/templates/ingredient_overview.html => wger/nutrition/templates/ingredient/overview.html
rename : wger/nutrition/templates/ingredient_search.html => wger/nutrition/templates/ingredient/search.html
rename : wger/nutrition/templates/view_ingredient.html => wger/nutrition/templates/ingredient/view.html
rename : wger/nutrition/templates/edit_meal_item.html => wger/nutrition/templates/meal_item/edit.html
rename : wger/nutrition/templates/nutrition_overview.html => wger/nutrition/templates/plan/overview.html
rename : wger/nutrition/templates/view_nutrition_plan.html => wger/nutrition/templates/plan/view.html
Calculate the nutritional values on the ingredient page
Add missing forms field
Fix PEP8 formatting errors
Add tests for the nutritional value calculator for ingredients
Calculate the nutritional values individually for plans, meals and meal items
Use better terms in the workout detail page
Split the views in the exercise app into individual files

--HG--
rename : wger/exercises/views.py => wger/exercises/views/categories.py
rename : wger/exercises/views.py => wger/exercises/views/comments.py
rename : wger/exercises/views.py => wger/exercises/views/exercises.py
Add interfaces to add and edit muscles

--HG--
rename : wger/exercises/templates/muscle_overview.html => wger/exercises/templates/muscles/overview.html