Fix UnicodeEncodeError when printing Field Conflicts
Fix UnicodeEncodeError when printing Field Conflicts

Fixed issue https://github.com/SchrodingersGat/KiBoM/issues/73 by:
* Adding `from __future__ import unicode_literals` to turn every string literal into a unicode string by default. Could just have pre-fixed offending strings with `u`, but noticed the precedent has been set in other source files, and saves missing a string.
* Appended `.encode('utf-8')` to (potentially Unicode) strings before passing to `print`. Necessary because `sys.stdout.encoding` is set to `None`, which causes Python 2 (the one included in the KiCad package) to default to trying to encode as 'ascii', which fails. Alternatively, could have changed the default encoding (either by via `PYTHONIOENCODING` environment variable, or with the `sys.setdefaultencoding` hack) but was scared away by the many, many warnings, such as here: https://stackoverflow.com/a/34378962/3697870
schneidersoft/KiBoM,SchrodingersGat/KiBoM,SchrodingersGat/KiBoM,schneidersoft/KiBoM