Hotfix: typographical errors

Error was `AttributeError: 'module' object has no attribute
	   'BitcoindError'`, reported in #554
Typographical Error

Credit: @faizkhan00
Removed Callback Functionality

Callbacks were never live on mainnet and would be much better
implemented in smart contracts.

- API Changes (see API ChangeLog)

Solves #552, #78
Only Overwrite Config File if Necessary
update fixtures
Typographical Error
update fixtures
Merge pull request #556 from ouziel-slama/develop

update fixtures
Hotfix: `AttributeError`
Updated Logging System

- Share logger across modules
- Shutdown logger gracefully
- Log logging level
- Simplify output
- Coloured output (for `WARNING`, `ERROR`, `CRITICAL`)
- Tweak logging of transaction skipping, decode errors

Also, did some minor reformatting of miscellaneous `import` statements.

Solves #533
Changed Default Timeout for python-bitcoinlib

- Went from 30 seconds to 120 seconds
Missing Line
Fixed API Status Poller

- API Status Poller wasn’t running at all!
- Improved logging of status polling
- Misc. bugs in `check.py`
Revert "Changed Default Timeout for python-bitcoinlib"

This reverts commit 50e846383c763f992a4f2fc3c0eb9e36011b20e4.
Set Socket Default Timeout

Solves #554
Measure How Far Behind the Backend is in Hours

Using seconds, as was done before, involved false precision.
Remove Unnecessary python-bitcoinlib Proxy
Hotfix: Never Share Backend Proxies

Solves #554
Never Share Backend Proxies

Solves #554
Revert "Set Socket Default Timeout"

This reverts commit 685e1f32afabbf48499241b0514535bb93f8a95f.