Updates to the latest version of the desktop client available. Tested
the config migration from `nextcloud-client` 2.3.3 with a Nextcloud
14.0.3 instance (hosted using `services.nextcloud`).
Additionally the derivation required the following changes:
* Dropped `Qt5Sql` patch: this has been fixed upstream and isn't needed
anymore (furthermore their CMake structure has changed and the patch
wouldn't apply anymore on 2.5.0).
* Moved to a new upstream repository (nextcloud/desktop), kept
`fetchgit` to properly fetch submodules.
* Added OpenSSL 1.1 integration: `libsync` (the syncing provided by this
package) requires 1.1, furthermore the linking flags had to be fixed
manually by passing `NIX_LDFLAGS` to the derivation.
Furthermore I moved the support for a Gnome3 keyring into its own
wrapper to avoid a full rebuild of the package whenever you alter
`withGnomeKeyring` in an override expressions.
It's still possible to enable keyring (now without recompile) like this:
```
nextcloud-client.override { withGnomeKeyring = true; }
```
To override the derivation itself you now have to use
`nextcloud-client-unwrapped`:
```
nextcloud-client-unwrapped.overrideAttrs (old: {
src = yoursrc;
})
```
`qtkeyring` can use `gnome-keyring`, but it needs some help to find it.
I have not enabled this by default because not everyone who uses this will want
to pull in GNOME dependencies.
