Fixes for the Nektar reader plugin.

Fixes are:
1) Had to add in PLUGIN_NAMES so that the plugin would be
available through the Plugin Manager.
2) Got rid of a bunch of compiler warnings.
3) Suppressed overloaded virtual methods warnings.

Change-Id: I355d27ae2dff5bda0db1f02c191e70b7e512fac1
Merge topic 'nektar_reader_plugin' into next

eb3fafe Fixes for the Nektar reader plugin.