Heatledger 0.9.15 - mandatory update

Heatledger 0.9.15

This is a mandatory update. Nodes below 0.9.14 will be blacklisted.

We especially ask medium to large stake holders to switch to this version preferably also
downloading the chain from the network.

Heatledger server 0.9.15 will do a hard fork at block 87,000. The fork at 87,000 will change the way
block generators validate order cancellations, the previous way that was done, in some cases,
was a cause for forks.

We've also changed the way public keys for accounts are stored and versioned, this was the other
reason forks used to happen.

With these two fixes combined we hope to have concluded the final solution for our forking issues.

Given the expected stability of this version we also already have hard coded block height 100,000
at which forging rewards will start again.

Work planned for these coming days might cause us to release another version before that but that
will most likely be an optional release which only involves the replicator database parts. So installing
this version should be enough to be able to start collecting block rewards again at block 100,000 which
will be seen in about 5 days from now.

[updated]