Use time instead of block for proposals

[fedekunze]

Description:

Text proposals use time instead of block. We will need to update PageProposal, LiProposal (use id instead of block);

// Text Proposals
type TextProposal struct {
	ProposalID   uint64       `json:"proposal_id"`   //  ID of the proposal
	Title        string       `json:"title"`         //  Title of the proposal
	Description  string       `json:"description"`   //  Description of the proposal
	ProposalType ProposalKind `json:"proposal_type"` //  Type of proposal. Initial set {PlainTextProposal, SoftwareUpgradeProposal}

	Status      ProposalStatus `json:"proposal_status"` //  Status of the Proposal {Pending, Active, Passed, Rejected}
	TallyResult TallyResult    `json:"tally_result"`    //  Result of Tallys

	SubmitTime     time.Time `json:"submit_time"`      //  Time of the block where TxGovSubmitProposal was included
	DepositEndTime time.Time `json:"deposit_end_time"` // Time that the Proposal would expire if deposit amount isn't met
	TotalDeposit   sdk.Coins `json:"total_deposit"`    //  Current deposit on this proposal. Initial value is set at InitialDeposit

	VotingStartTime time.Time `json:"voting_start_time"` //  Time of the block where MinDeposit was reached. -1 if MinDeposit is not reached
	VotingEndTime   time.Time `json:"voting_end_time"`   // Time that the VotingPeriod for this proposal will end and votes will be tallied
}