Default click options per chain

[NIXBNT]

Addresses #543

Adds a set of default parameters for each supported blockchain to the constants.py

WARNING

1. These defaults need to be checked thoroughly prior to merge @barakman @Lesigh-3100
2. In order to use uniswap_v2_forks for the default input of each exchange I was required to remove 'uniswap_v2' from being explicitly added to the forks list (as it doesnt appear on every chain). We need to verify this doesnt have any adverse effects @Lesigh-3100 thoughts? Alternatively, we can go back to specifying each supported exchange explicitly in the defaults