Resolve "Prevent voting during budget finalization"

See merge request crown/crown-core!109

Unit tests for CFinalizedBudget

See merge request !104

Unit test compilation fix with gcc 4.8

See merge request !107

Merge branch '139-impl-finalbudget-order-agnostic-comparison' into 142-prevent-voting-during-finalization

Merge branch '139-impl-finalbudget-order-agnostic-comparison' into 142-prevent-voting-during-finalization

CBudgetManager::UpdateProposal() now checks if the vote timestamp
is within 75% of estimated time before the superblock (2880 blocks
times 1 min in mainnet). If not - vote is rejected.

* CBudgetManager::SubmitProposalVote() is added
* SubmitProposalVote is used in rpc-masternode-budget.cpp to submit
  new votes for proposals. UpdateProposal is used now only to add
  votes received through the network
* SubmitProposalVote and UpdateProposal got draft implementation
  of prvention of voting during budget finalization
* Some unit tests added