WIP: Localchain feature

[adizere]

Closes: #158 (not ready!)

Before merging:

• This depends on tendermint-rs commit 3298d63 being released.
• Remove the git options from the cargo's toml files and pin against a release.

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For contributor use:

• Unit tests written
• Added test to CI if applicable
• Updated CHANGELOG_PENDING.md
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Updated relevant documentation (docs/) and code comments
• Re-reviewed Files changed in the Github PR explorer

[adizere]

This PR is currently on hold. Partly because this is blocked on tendermint-rs side, partly because fixing cosmos/ibc-rs#111 takes priority for the moment.

[codecov-io]

Codecov Report

Merging #289 into master will increase coverage by 23.3%.
The diff coverage is 66.3%.

@@            Coverage Diff            @@
##           master    informalsystems/hermes#289      +/-   ##
=========================================
+ Coverage    13.6%   37.0%   +23.3%     
=========================================
  Files          69     129      +60     
  Lines        3752    8390    +4638     
  Branches     1374    2905    +1531     
=========================================
+ Hits          513    3106    +2593     
- Misses       2618    5105    +2487     
+ Partials      621     179     -442     

Impacted Files	Coverage Δ
modules/src/events.rs	0.0% <0.0%> (ø)
modules/src/ics02_client/events.rs	0.0% <ø> (ø)
modules/src/ics02_client/raw.rs	0.0% <0.0%> (ø)
modules/src/ics03_connection/error.rs	13.6% <0.0%> (-19.7%)	⬇️
modules/src/ics04_channel/error.rs	75.0% <ø> (+50.0%)	⬆️
modules/src/ics04_channel/packet.rs	0.0% <0.0%> (ø)
modules/src/ics07_tendermint/client_def.rs	0.0% <0.0%> (ø)
modules/src/ics07_tendermint/error.rs	75.0% <ø> (+75.0%)	⬆️
modules/src/ics18_relayer/error.rs	0.0% <0.0%> (ø)
modules/src/ics26_routing/error.rs	75.0% <0.0%> (ø)
... and 237 more

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[adizere]

We're abandoning this PR in favor of two smaller ones. We'll have one PR that focuses exclusively on modifications for the ibc crate (#390), plus another PR where we'll add the localchain feature itself (mostly modifications in the relayer and cli crates).