Make config and paths work for MCS

[ch-williamson]

Relevant comments from code review:

• config

we'll have to transfer all the config information into base_config.py since packages don't include any data files

from config import base_config
BUCKET_NAME = base_config.BUCKET_NAME
INSTALLATIONS_RAW_S3_PATH = base_config.INSTALLATIONS_RAW_S3_PATH

• paths

we'll have to go through and adjust all data paths so they have the same format throughout. I recommend having a data path that would lead to the ASF core data in a local dir or directly to the S3 bucket, and then a relative path that leads to the specific file. That way we can easily pick whether we want to load it from S3 or local dir, and give the relative path as default values using the config file.

also, EPC in joining script:

        epcs = asf_core_data.getters.epc.epc_data.load_preprocessed_epc_data(data_path='S3', 
            version=epc_version,
            usecols=[relevant features you need for this, defined in base_config.py],

• refresh - consider how this should work across the package