feat(RD): add texture pack downloader

This extends the resource pack downloader, with the custom behavior of
filtering the versions that shows up, to those <= 1.6. As always, Flame
is funky and requires a bit more workarounds than average.

This will also get a nice improvement when the Version parsing and
comparison PR gets merged! :D

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/meta/Version.cpp

@@ -99,6 +99,11 @@ QString Meta::Version::localFilename() const
     return m_uid + '/' + m_version + ".json";
 }
 
+::Version Meta::Version::toComparableVersion() const
+{
+    return { const_cast<Meta::Version*>(this)->descriptor() };
+}
+
 void Meta::Version::setType(const QString &type)
 {
     m_type = type;