Broken Sanity Check; Miscellanea

- Ignore pure BTC transactions for `transaction.construct()` Sanity
  Check (necessary, now that `get_tx_info2()` raises a `DecodeError` on
  them). Solves #558.

- CLI arguments for callable assets were not properly handled.

- Updated ChangeLog

- Misc. minor bugs
More Elegant Skipping of Pure BTC Transactions

Now, the sanity check in `transaction.construct()` only skips
transactions which raise a particular BTC‐only exception. The use of
such an exception distinguishes transactions that cannot be parsed from
ones that simply shouldn’t be. (The former type should be caught by the
sanity check.)

Solves #558.
One Proxy Per Thread, Passed Around as Parameter

Solves #554. (I’m pretty sure.)
Fixed Bug Introduced with Recent Logging Updates

- Typographical errors
- Needed to change level of *root* logger (and then change it back)

Solves #560.
Always use get_cached_raw_transaction().
BTW fixe tests.
Merge pull request #561 from ouziel-slama/develop

Always use get_cached_raw_transaction().