Make it possible to monitor addresses for transactions

[boumanb]

It should be able to add addresses to the application.
At this moment it is taking way too long to search through all blocks and their transactions everytime.

The application should save all the relevant transactions into the database. And this transactions should be up to date most of the time.

e.g. if someone requests all the data that is sent to one address, the data should be already in the database or should be only requested once.

ALSO POSSIBLE (to move around saving data):

Save all the references to relevant transactions and load them in javascript while page is loading. This will also save a lot of time. And data comes straight from the blockchain.