Add metadata writing to new ingestion routines.

[samueljackson92]

Cannot be merged before #46

This adds the ability to write out the metadata from each source while performing the ingestion

To test:
You can test by running an ingestion looking at the produced '*.db' file.

You can take a peak a the file like so:

import pandas as pd
import sqlite3
con = sqlite3.connect('metadatabase.db')
df = pd.read_sql('select * from signals WHERE shot_id=50900', con=con)
print(df)
df = pd.read_sql('select * from sources WHERE shot_id=50900', con=con)
print(df)