Add back fixes that were in Singularity (in indra/media_plugins) but not
in imprudence.
Also:
Add "shutdown" plugin message and terminate file picker plugins cleanly.
The DSO (libbasic_plugin_filepicker.so) now tells the child process /
plugin loader (SLPlugin) to terminate (using the 'shutdown' message),
and AIFilePicker::finish_impl destroys the plugin object on the viewer
side when it's ... finished thus.
Also added a large comment that gives an overview of all classes
involved on the viewer side.
Additional fixes for filepicker.
Plugin refactor bug fix: mDeleteMe was uninitialized in AIPluginFilePicker.
This commit deletes all indra/media_plugins and copied one-on-one
the indra/plugins directory from my (imprudence) statemachine branch
(which contains the AIFilePicker patch).
git shows this as a lot of 'renamed' files because originally it
was a rename. However, there are a lot of changes as well: it's both
an upgrade to a newer plugin system (changes by LL) as well as an
upgrade to my refactored plugin system with a file picker as plugin.
Since this commit is a one-on-one copy, it disregards any changes
that were in Singularity and not in imprudence in indra/media_plugins
however. I will add those back in the next commit.
