Log:
Never modify the value of CMAKE_INSTALL_PREFIX after including GNUInstallDirs ，Otherwise incorrect CMAKE_INSTALL_FULL_XXXX values will be computed
Modify project to pass the REUSE check
Log: Modify project to pass the REUSE check
Task: https://pms.uniontech.com/task-view-185215.html
Change-Id: Ie954cf985f16c1a243bfc912aa7458c6e85ce9de
Note:
1. add a new function in PluginProxyInterface for set applet widget
visible from a plugin.
2. remove requestContextMenu function from PluginProxyInterface,
cause's the context menu should be handled in Dock, it is enough for
a plugin to simply provide menu data and handle callbacks with
functions itemContextMenu and invokedMenuItem in PluginsItemInterface
https://github.com/linuxdeepin/internal-discussion/issues/646
Change-Id: Ic4af4eee138e87911ff5b18ccbbb0c3f7187ac4d
