make path of levelDB database configurable

[kautukkundan]

Problem

Currently the path of levelDB folder is hardcoded. It may not be ideal for every user to keep the same path for the database and they might need to set it somewhere else.

Solution

Add levelDB folder path in the config so that it is easily changeable. Additionally, it'll better to have separate path for DB while running tests so that it doesn't interfere with DB running in production. Right now the tests wipes the contents of levelDB folder completely.