Database information made private

Affected files:
  taxi/.gitignore
  taxi/application/config/database.php

Requirement:
- In taxi/application, create a file "db_config.txt"
- In the file, write the following:
    username=<your username>;
    password=<your db password>;
    database=<database name>;
- e.g.
    username=root;
    password=nnnn;
    database=taxi_reporting_ph;