Feature: Database Connection

astroAPIServer only supports database interfaces specified by Python's DB-API v2.0 ([PEP 249](https://www.python.org/dev/peps/pep-0249/)). Such python interfaces includes the following python packages:

* sqlite3
* pymysql
* psycopg

## Design Choices
* astroAPIServer relies solely on Cursor objects and it is up to the users to establish the Connection object.
* astroAPIServer will not support any connection methods beyond what's specified in DB-API v2.0.

## Issues
* astroAPIServer will need to deal with various placeholder syntaxes. Two options are possible
1. User defines the placeholder attributes.
2. astroAPIServer defines placeholder for at least the most popular DB-API packages and placeholders.

## Usage
For example, let's using sqlite3. We instantiate the cursor object by some function `get_database`,

```python
# database_handler.py
def get_database(database):
db_path = "/path/to/database.db"
con = sqlite3.connect(db_path)
cursor = con.cursor()
return cursor
```

astroAPIServer is built with both the Flask object and `get_database`.

```python
from flask import Flask
from database_handler import get_database

app = Flask(__name__)
api = API(app, get_database=get_database)
```

Start with the database_handler.py example and the get_database entry point, then review how API(app, get_database=get_database) is intended to use cursor objects. The issue leaves the placeholder-syntax choice and implementation scope unresolved; done criteria would need to define supported DB-API packages and how their placeholders are handled.

Written by the indexing model from the issue text.