Renamed Darkcoin to Dash

[crowning-]

"Darkcoin" was recently renamed to "Dash", see https://www.dashpay.io/news/darkcoin-is-now-dash/ .
I have implemented this change.

Additionally I have increased the the length of the database representation of the currency string by one (chain_code3 is now VARCHAR(5)) to allow 4-character currency names there.

Due to the way VARCHAR() is implemented this is fully backward compatible.

People who already have Abe running for the old "Darkcoin" blockchain need to do the following steps to make it run as "Dash":

1. delete blocks- and chainstate-folders from .dash
2. re-sync the Dash blockchain from scratch
3. delete the complete Abe-database, e.g. when you use mysql:
   • connect to database: mysql -u root -p
   • delete database: drop database abe;
   • create it again: create database abe;
   • give user abe the permissions again: grant all on abe.* to abe;
4. rebuild the Abe-database: python -m Abe.abe --config abe.conf --commit-bytes 10000 --no-serve

It's important to connect to the database as user "root". I tried it with user "abe" first and it did NOT correctly rebuild Abe's database.

The configuration file for Abe (abe.conf) should have the following datadir entry:

datadir = [{
        "dirname": "/home/<username>/.dash/",
        "chain":   "Dash",
        "code3":   "DASH",
        "address_version": "\u004c" }]

[jtobey]

A couple minor issues. The files are made executable (100644 → 100755). Please put them back to 644. Please put the genesis hash and tx back in its old position in genesis_tx.py so the diff shows only the change to coin name.
Thanks.

[crowning-]

Re-ordered for minimal diff and file permissions set to 644.

Sorry for the permission thing, I guess the text editor did this :-/
Should have used what I normally use, vi :-)