Fetch product categories Eagerly

OPEN - task 24: Create a stock module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/24
Fix #61 by eagerly fetch categories

Merge branch 'iss61-product-categories-lazy-init'
Merge branch 'iss61-product-categories-lazy-init' into develop
Set grow=false for Categories display column
Minor Changes: ProductDetails Layout

Merge branch 'develop'
Merge pull request #75 from TheKojuEffect/master

Display Categories of Product in ProductDetails correctly