[FR] Improve Error Message For Unknown Aggregation Method Error

[SJrX]

Is your feature request related to a problem? Please describe.
I was switching over to go-carbon and had a typo in my storage-aggregation.conf file, I had aggergationMethod instead of aggregationMethod. This had kind of worked fine with the python version. However when I started up go-carbon I just got an error that said "unknown aggregation method ''", which made no sense to me.

I "knew" the file worked with carbon, so I thought it was a bug, but had to clone the repo and run it with debugging to debug.

Describe the solution you'd like
A slightly better error message

Additional context
I guess in other cases line numbers would be useful, but that didn't seem like an easy refactor in the code.