Refactoring: Created hscommon.desktop

This unit hosts previously awkward UI view methods which weren't related
to the view itself, but to the current desktop environment. These
functions are now at their appropriate place.
Updated hscommon
Updated cocoalib
Merge branch 'master' into develop
Fix boken tests
Merge branch 'master' into develop
Fixed appdata logic which was broken on OS X.
On OS X, read Exif tags using Cocoa's built-in functionality

This allows for RAW files Exif reading. Fixes #234.
Fixed build on OS X which was broken
Fixed compilation warnings on OS X
Fixed tests which were broken
Refactoring: Path API compatibility with pathlib

Refactored dupeGuru to make hscommon.path's API a bit close to pathlib's
API. It's not 100% compatible yet, but it's much better than before.

This is more of a hscommon refactoring than a dupeguru one, but since
duepGuru is the main user of Path, it was the driver behind the
refactoring.

This refactoring also see the introduction of @pathify, which ensure
Path arguments. Previously, we were often unsure of whether the caller
of a function was passing a Path or a str. This problem is now solved
and this allows us to remove hscommon.io, an ill-conceived attempt to
solve that same ambiguity problem.

Fixes #235.
Reorganized hscommon documentation

Removed hscommon's "docs" folder and moved all documentation directly
into docstrings. Then, in dupeGuru's developer documentation, added
autodoc references to relevant modules.

The result is a much more usable hscommon documentation.
Greatly improved docs

Added a new scan.rst page, laying out in much more details than before
the inner workings of the scanning process.

Fixes #208, but does much more than that.
Merge branch 'master' into develop
Make non-numeric delta comparison case insensitive

Fixes #239.
Make Cmd+A select all folders in the Folder Selection dialog (Cocoa)

Fixes #228.
pygettext: explicitly open files as utf-8

When running it through SSH, I couldn't open files with non-ascii chars.
Improved hscommon.gui docs
Improved hscommon.gui docs

Added docs for Table and Row in hscommon.gui.table.