#161413448 Implement models for the api endpints

[mugoh]

What does this PR do?
Change the organisation of the development files by separating the models and views.

Description of Task to be completed?
Have all resource models in separately named files
Have all views for resources in different files, each on it's own
Hold the views_files in a view folder
Th model files in another

How should this be manually tested?
Clone the repo and cd into it.
Run the flask app and test GET and POST endpoints on the paths below:
'stman/api/v1.0/sales'
'stman/api/v1.0/products'

What are the relevant pivotal tracker stories?

#161413576
#161413600
#161414982
#161414536

[coveralls]

Pull Request Test Coverage Report for Build 72

• 0 of 16 (0.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-10.5%) to 85.714%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
app/api/init.py	0	3	0.0%
app/api/app.py	0	13	0.0%

Totals
Change from base Build 57:	-10.5%
Covered Lines:	132
Relevant Lines:	154

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💛 - Coveralls