Moves all things related to creating the URLs of the mod platforms
that go to network tasks to a single place, so that:
1. Maintaining and fixing eventual issues is more straightforward.
2. Makes it possible to factor out more common code between the
different modplatform pages
This creates a hierarchy in which ModPage and ModModel are the parents
of every mod provider, providing the basic functionality common to all
of them.
It also imposes a unique .ui file (they were already equal before, just
duplicated basically) on all mod providers.
Fixes#206 partially. Although we don't list mods that have no
compatibility with the mod loader we are using, mods that have support
for both loaders still show up, and the versions for both the loaders
are still shown.
Also simplifies a little the logic in
FlameModIndex::loadIndexedPackVersions
When selecting multiple mods at once, it can become hard to keep track
of which ones you selected.
To address this, a dialog is now displayed
when you finish selecting the mods to download, showing you which ones
you selected and their filenames. From there, you can either accept it
and download the mods, or you can cancel it and go back to the mod
selection dialog.
Previously, we used a unique_ptr to a ModDownloadTask to keep track of
the selected mod to download when we accepted the dialog.
In order to allow multiple mods to be selected at once for download,
this has been changed to a QHash where the key is the mods name (since
it doesn't seem right to allow for multiple versions of the same mod to
be downloaded at once), and the value is a pointer to the corresponding
ModDownloadTask.
Let's move off our custom QuaZip. In the olden times we needed the
custom version of QuaZip, as it was basically unmaintained and on
SourceForge (eww). But nowadays it's maintained and on GitHub. See
new GitHub page: https://github.com/stachenov/quazip
