Fix installation of Marketplace packages on Windows

The installation of packages from Nuxeo Marketplace is not correctly completed is some cases when the installer needs to remove old plugins: when using Windows, the process running Nuxeo is holding a lock on the jar files under nxserver/bundles what prevents from removing them after the installation of a hot fix for example.

A workaround is to remove manually the old plugins from nxserver/bundles.

As a matter of fact, hot reload may also not work on Windows.