Remove dbcache option, flowee doesn't need it.
This is a legacy option that was needed when the leveldb layer was
used for the utxo, as that required us to write our own caching.
So, now we install the example config file
Then we follow XDG for retrieving it.
We first check XDG_CONFIG (~/.config/flowee) and if we can't find a confg
file there fall back to the data dir (~/.local/share/flowee).
TomZ