3.0.6.2: Electrum-FTC bugfix for testing release

Changelog:

• workaround for old PyQt5 versions
• fixed issue with invalid WIF keys
• fixed copy&paste error in README

Note: This version has had no previous public exposure
and therefore some issues might be discovered during
everyday usage. In general, no major flaws are expected
because the wallet code only slightly differs from
vanilla electrum.