* Added `from __future__ import unicode_literals` to every file so
now all strings in code are forced to be unicode strings unless
marked as byte string `b'str'` or encoded to byte string `'str'.encode('utf-8')`.
This is a large change but we have been working towards the goal of unicode
strings passed in the code so decoding external input and encoding
output as byte strings (where applicable).
Note that in Python 2 the `str` type still refers to byte strings.
* Replaced the use of `str` for `basestring` in isinstance comparison as
this was the original intention but breaks code when encoutering unicode strings.
* Marked byte strings in gtkui as the conversion to utf8 is not always handled, mostly
related to gobject signal names.
* A rather disruptive change but for a few reasons such as easier to read,
easier type, keep consistent and javascript code uses single quotes.
* There are a few exceptions for the automated process:
* Any double quotes in comments
* Triple double quotes for docstrings
* Strings containing single quotes are left e.g. "they're"
* To deal with merge conflicts from feature branches it is best to follow
these steps for each commit:
* Create a patch: `git format-patch -1 <sha1>`
* Edit the patch and replace double quotes with single except those in
comments or strings containing an unescaped apostrophe.
* Check the patch `git apply --check <patchfile>` and fix any remaining
issues if it outputs an error.
* Apply the patch `git am < <patchfile>`
