* PIP Table Cost relative to average peers instead of max peers

* Add tracing in PIP new_cost_table

* Update stat peer_count

* Use number of leeching peers for Light serve costs

* Fix test::light_params_load_share_depends_on_max_peers (wrong type)

* Remove (now) useless test

* Remove `load_share` from LightParams.Config
Prevent div. by 0

* Add LEECHER_COUNT_FACTOR

* PR Grumble: u64 to u32 for f64 casting

* Prevent u32 overflow for avg_peer_count

* Add tests for LightSync::Statistics

* Don't send empty step twice or empty step then block.

* Perform basic validation of locally sealed blocks.

* Don't include empty step twice.

* Add `is_idle` to LightSync to check importing status

* Use SyncStateWrapper to make sure is_idle gets updates

* Update is_major_import to use verified queue size as well

* Add comment for `is_idle`

* Add Debug to `SyncStateWrapper`

* `fn get` -> `fn into_inner`

* ci: rearrange pipeline by logic

* ci: rename docs script

* Update Dockerfile

Since parity is built for "mission critical use", I thought other operators may see the need for this.

Adding the `curl` and `jq` commands allows for an extremely simple health check to be usable in container orchestrators.

For example. Here is a health check for a parity docker container running in Kubernetes.

This can be setup as a readiness Probe that would prevent clustered nodes that aren't ready from serving traffic.

```bash
#!/bin/bash

ETH_SYNCING=$(curl -X POST --data '{"jsonrpc":"2.0","method":"eth_syncing","params":[],"id":1}' http://localhost:8545 -H 'Content-Type: application/json')
RESULT=$(echo "$ETH_SYNCING | jq -r .result)

if [ "$RESULT" == "false" ]; then
  echo "Parity is ready to start accepting traffic"
  exit 0
else
  echo "Parity is still syncing the blockchain"
  exit 1
fi
```

* add sync check script

* Dockerfile: change source path of the newly added check_sync.sh (#9869)

* Do not create a home directory.

* Re-add -m flag

* bump smallvec to 0.6 in ethcore-light, ethstore and whisper

* bump transaction-pool

* Fix test.

this makes sure we no longer depend on smallvec 0.2.1 which is
affected by servo/rust-smallvec#96