integrate time locks - Githubissues

PR #107 adds support for time locks, but several integration-related tasks remain.

[x] test that un-time-locked UTXOs can be spent
[x] test that time-locked UTXOs cannot be spent if the release date is in the future
[x] test that time-locked UTXOs can be spend if the release date is in the past
[x] test that premine recipients cannot spend their time-locked coins before the release date
[x] test that premine recipients can spend their time-locked coins after the release date
[x] modify balance calculator: count only spendable UTXOs
[x] add balance calculator for time-locked UTXOs
[x] modify transaction compiler: select only spendable UTXOs
[x] test that compiling a transaction that spends too much fails, even if spendable balance + time-locked balance is enough
[x] add CLI command to list all UTXOs with release dates and display amounts, with totals
[x] display time-locked balance in dashboard

Neptune-Crypto / neptune-core