Agree on Parity configuration options

[weilbith]

Due to #493 the different locations where we defined configuration options for Parit have been merged into a single file. This includes the options of the former validator-config.toml file. These were not used before, since the Docker image only extended the user-config.toml with own snippets and additional parameter. The "new" options of the validator configuration must be decided on, if we actually want them and if they should be applied for validators only (comment them out per default). The diff of new options which weren't used before is the following (this ignores the author option, which is part of #533):

[parity]
# Save pending local transactions to disk to be restored whenever the node restarts.
no_persistent_txqueue = false

[network]
# Parity will maintain at most 100 peers.
max_peers = 100

[mining]
# New transactions will not cause a new pending block to be created.
reseal_on_txs = "none"
# Minimum amount of Wei per GAS to be paid for a transaction to be accepted for mining. Overrides --usd-per-tx.
min_gas_price = 1
# Maximum number of transactions per sender in the queue. By default it's 1% of the entire queue, but not less than 16.
tx_queue_per_sender = 100

[weilbith]

This should be discussed at the end of the today's daily meeting.

[weilbith]

Result:

• no_persistent_txqueue -> remove
• max_peers -> remove
• reseal_on_tx -> remove
• min_gas_prize -> to be clarified (if @andfletcher don't care we go for 1) [ @cducrest will ask]
• tx_queue_per_sender -> 100

[cducrest]

We agreed and will be using min_gas_price = 1000000000 so that it corresponds to 1 GWei.