Some improvement to agents//view and agents//trade.

Added messages if no trades have been made or if the portfolio is
empty.

Added a refresh button to refresh the status of the agent.

Added a button to navigate from trade to view.
Added auto-refreshing to trade and agent views.

This required the addition of angular-timer to bower, so an npm install
is needed.
Moved cash into composition of portfolio.
Secured against an agent trying to trade cash.
Added a 'reset trades' button to the agent view.