Squash-merged on request.
* Dogecoin address prefixes
* Use "doge" for BECH32 addresses
* Switch Bitcoin references to Dogecoin in Travis
* Update addresses in dogecoin-tx tests
* Use "doge" for BECH32 addresses
* Remove functional tests which do not apply to Dogecoin (backwards compatibility tests do not have suitable clients to test against)
When extra entropy is not specified by the caller, CKey::Sign will
now always create a signature that has a low R value and is at most
70 bytes. The resulting signature on the stack will be 71 bytes when
the sighash byte is included.
Using low R signatures means that the resulting DER encoded signature
will never need to have additional padding to account for high R
values.
