Remove broken demo environment download
DISTRO-506 Allow specifying HBase master port

Allow specifying the HBase master webui port manually
with the SEP monitoring tools. The SEP tools load the HBase config
from the HBase master webui, making the webui port the only
thing that would possibly need to be manually specified.
DISTRO-505 Validate config settings before startup

Validate configuration settings before staring an hbase-indexer
server. This allows quickly avoiding the situation where indexes
can be created with invalid HBase settings.