Revise hierarchy for databases

Previously all databases in data_dir/chain were lumped in the same
directory. Now they are split up with the raw chain in data_dir/

The application checks if this conversion needs to be performed on
startup and moves the directories to the new locations if necessary.
Resolve #303

The database can be rebuilt now with the --rebuild-index argument, which
will rebuild the database without deleting or re-downloading the
blockchain.
Merge branch 'master' of github.com:BitShares/bitshares_toolkit

Conflicts:
	libraries/blockchain/chain_database.cpp
Resolve #303

Fix some remaining problems with the solution for rebuilding the database index without redownloading the blockchain.
Merge branch 'master' of github.com:BitShares/bitshares_toolkit