Support installation of the bzip2 plugin under name libh5bzip2.so

[DennisHeimbigner]

re: #1347

It turns out that the plugin libraries (bzip2 and misc) were
being installed as part of 'make install'. This was not intended
behavior. But after some discussion in the above issue, it was decided
to install the bzip2 plugin. However, in order to avoid naming conflicts,
the plugin is installed under the name 'libh5bzip2.so'.
Note that this is automake behavior only; the install does not
(yet) occur using cmake.

Misc. unrelated changes

1. turn off some debug output in ncdump/Makefile.am

[edhartnett]

In your plugins, do you have a full implimentation of szip library?

If so, should this just be something we require at configure and not ship it?

[DennisHeimbigner]

In your plugins, do you have a full implementation of szip library?

You said szip; I assume you mean bzip2. And yes, there is complete bzip2
compress/decompress code in the plugins directory and is part of the
distribution.

[opoplawski]

Plugins (i.e. dlopened libraries) should not be installed in $libdir, but in something like ${libdir}/netcdf - i.e. a custom directory for plugins.

[DennisHeimbigner]

Good idea; then we can avoid using a weird name for the plugin.

[WardF]

Thanks @opoplawski, I agree with @DennisHeimbigner . We will see what we can do.