Fixed ReleaseData functionality in algorithms.

It turns out that ReleaseData has been broken for a while, in
that it didn't release data. No test looked at this so nothing
failed. Fixed. I also added a test. As Bill Lorensen always
says "if it is not tested, it is broken"

Change-Id: Iae817886d5dca88752df6c6f5496bb229b6ea43f
Major reworking of vtkMultiBlockPLOT3DReader.

Added lots of new functionality including:
- Support for OVERFLOW files,
- Support for double precision,
- Auto-detection of the format of binary files.

Also cleaned up the code significantly.

Change-Id: I13a18c1afce8e3587529a385599084943f3f4143
Added a new reader to better handle PLOT3D files.

- Added a new reader (vtkPlot3DMetaReader) designed to make it easier
to deal with Plot3D files. This is a meta-file in which the user
can specify various settings (such as endianness, multi-grid etc.)
rather than having to do it through the reader API. The reader also
supports time series of xyz and q files.
- Added JSON CPP support which is used by the meta-reader.

Change-Id: I991e6487869966c3e1769835a72fd2f8b7f81770
Merge topic 'release-data-fix' into master

6c965828 Fixed ReleaseData functionality in algorithms.
Merge topic 'plot3d-reader-improvements' into master

50e677ac Major reworking of vtkMultiBlockPLOT3DReader.
Merge topic 'plot3d-meta-reader' into master

452d8812 Added a new reader to better handle PLOT3D files.
Fixed compiler warning about signed/unsigned int comparison.

Change-Id: Icf4e6788ade7f4ea6ee2b13d63ffee2a08fbae20
Merge topic 'fixed-warning' into master

98100c99 Fixed compiler warning about signed/unsigned int comparison.