default contracts & configs

[zeroXbrock]

• add contracts under testfile crate
• add module default_templates to generate TestConfig templates that can be used as starting points or full test configs
• add DefaultConfig enum which configures preset examples (one test case FillBlock included)
• add template command to CLI to write templates from default_templates to testfiles

example: fill blocks with as much gas as possible

# in contender/cli:

# this will create testfile.toml by default. To change it, add flag '-o <filename>'
cargo run -- template -b fillblock -r http://localhost:8545
cargo run -- setup ./testfile.toml http://localhost:8545 -p 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80
cargo run -- spam ./testfile.toml http://localhost:8545 -p 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80 --tpb 2 -d 3

[zeroXbrock]

nope, don't need all these submodules