* Drop nBudgetProposalEstablishingTime
* Refactor: replace `== COutPoint()` with `.IsNull()`
* Refactor: add `operator bool()` to CMasternodePing
* Refactor: actually use `operator bool()` for CPendingDsaRequest
* Refactor: fixing code style in TrafficGraphData
* Fix some comments and whitespaces
* Drop CGovernanceVote::GetTypeHash()
* Drop legacy X11 code
No longer used... if it ever was used at all.
* Move `<boost/foreach.hpp>` out of coins.h
* Simplify CMasternodeBlockPayees::GetRequiredPaymentsString()
Also less of boost::lexical_cast
* Drop CTxDSIn::nSentTimes
* Fix few warnings
* fix warning (timer)
* fix nit
* reserve colateral keey only if needed
reserve colateral keey only if needed -> fix losing one key on every
subsequent CreateDonominate
* Adding KeyHolder and KeyHolderStorage
Adding KeyHolder and KeyHolderStorage to store keys used in PrivateSend
until status of mixing is known.
* Removing ClearOn... methods. Instead of calling directly KeepAll/ReplaceAll.
* remove usage of shared_ptr
* use unique_ptr
* follow naming convention
* use CKeyHolderStorage in CreateDenominated too
* adjust log messages
* return keys on POOL_STATE_ERROR, keep keys on POOL_STATE_SUCCESS
* Disable copy/assign and allow move
* Use keyHolderStorageDenom for collateral output in CreateDenominated
