Updated online/offline event checks so they are run during initialisation.
Updated online/offline event checks so they are run during initialisation.

Changed the online event to `once` and set it to be bound every time the node goes offline.

The above changes handle the case where:
1) `embark run` runs and starts geth.
2) geth is killed manually
3) `embark blockchain` is run in separate process to restart geth
4) the `embark run` process detects this change and restarts the web3 provider and recompiles/deploys/builds

Every time `embark blochain` is restarted, an error is appended and all are emitted from the `eth-block-tracker`. This is a bug but can't figure out where it originates. The downside is that if, for example, `embark blockchain` is restarted 4 times, there will be 4 errors emitted from the `eth-block-tracker`. Because of this, errors emitted from `eth-block-tracker` have been reduced to trace to avoid clogging the logs.

iurimatias/embark-framework,iurimatias/embark-framework