* Clean server shutdown, generalizes usage of `Weak`. Introduces 2 main changes:
* A shared `AtomicBool` that signals server shutdown. All server
threads regularly check it to break out of their main loops when
it changes to `true`.
* Breaking of circular `Arc` references, which can never be
destroyed, by downgrading to `Weak` instead. Only the main server
keeps the `Arc` while all other components get the `Weak` variant.
Both of these are required for all long-living structs to be
cleanly destroyed. Note that in Rust this is fairly important as
most resource-freeing logic is associated with `drop`,
which is only called when said struct is free of scope or `Arc`
references.
Should address most of #536 (only need the stop hook to call
`Server` shutdown).
* Test for fast sync, followed by restart, followed by re-fast-sync
* P2P test fix
* Double sync taking too long for Travis, commenting out for now
* First tests for API handlers
* Test chain UTXO handler
* Add test sumtrees handlers
* Fix typo
* Removed unused logger
* Update bitflags to ^1.0
* Missing test for bitflags update
* Moved test to grin directory
* Remove tests dependencies
* Add API P2P tests
* Fix hex string commitment
* Fix conflicting port
* Fix directory conflict and server port
* Wait for at least one block is mined on Travis
Ignotus Peverell