Added the ability for our pipedrive API client to store tokens.

## Purpose
Pipedrive's API requires a token in order to function properly. We can either provide this token on our own (if API access is on behalf of a system) or give pipedrive some user credentials in order to obtain a token (if API access is on behalf of a user). This change set creates the ability for our Pipedrive API client to keep a copy of a token given to it. If user credentials are given to it instead, we retrieve an API token from the pipedrive API using these credentials.