Fix #224

Since we don't enforce uniqueness on group names anymore

Which will have to use when linking associated files, as we won't have a
fileId during the discovering phase.
refs #102

Always use '/' for directory separators, and accept '\' on win32

Since we don't ignore any row, might as well not keeping an explicit
indexing.
Also, add an assertion about no other columns being left in the row

when fetching folder but joining with other tables

Fix #221

Instead of running them for each push (and most likely each tags, given
that gitlab-ci default `only` to `['branches', 'tags']
https://docs.gitlab.com/ee/ci/yaml/#onlyexcept-basic

In order for the vlc prebuilt versions to contain the fixes required for
!238 & #216

fix #218

refs #218

refs #218

refs #218

refs #218

refs #218

fix #209

refs #218

Since they won't be detected afterward, they won't be converted to
internal media, and the test will fail

There's no point in having a try block when the condition is false, so
invert the if & try to avoid handling exceptions for nothing

Instead, fetch the row fields, and update the mrl only. Otherwise, we
can't edit the Task schema as we'd fail to load any task using the
updated task class with an outdated database schema

This is the only class doing it, it clutters the code for not much
gain, and would enforce unique constraint we don't need for the backup
table

fsDir can't be null, as createDirectory always returns an IDirectory
instance