Make Frequency and Phase internal ivars be vectors.

In preparation for the support of multiple mode files, each of which
will have its own frequency.

Change-Id: Ib376d22270ea86b6cc61cdfd20911dfbb4462bd6
Change vtkSLACReader::ReadFieldData interface for multiple modes.

This is in preparation for implementing the ability to read in multiple
modes and combine them together.  Currently, only one mode is passed and
one mode looked at.

Change-Id: I2a75ac235024aad89365e63c95a05dd65ca0c6dd
Add ability to open multiple mode files in vtkSLACReader::RequestData.

This includes changes to allow copying the NetCDF file descriptor
manager object.

Although RequestData will happily pass multiple modes to ReadFieldData,
this latter method still only handles one mode at a time, and currently
asserts if you actually try to open multiple modes.  That will be
updated soon.

Change-Id: Ic0b5accc6874a5b7e06bb6f1f8488ab92aa2d07d
Move array reading inside of conditionals.

This is because in exactly one condition the reading will have to be
done in a loop.

Change-Id: I9fc60ba570f57e0a4ccb51a52101cb9a0ddc486a
Accumulate multiple modes together in SLAC reader.

Change-Id: Ic2da813208c1b07275eccb38db2c997e6472144a
Add test for multiple modes in SLAC reader.

Change-Id: I46e6257f1db43b259187e620e35d4c5c1ea79376
Add ability to adjust amplitude and phase of SLAC reader modes.

Change-Id: I959e7d4af1ce349f83bf273a1a423f135679fd73
Adding API to make it easier to access properties in ParaView.

Change-Id: I9bb96ef1cd059fc3ad4944af10352fcefa559e89
Merge topic '13374-slac-multiple-modes' into master

97343c1d Adding API to make it easier to access properties in ParaView.
0a3c83c4 Add ability to adjust amplitude and phase of SLAC reader modes.
4fecd59e Add test for multiple modes in SLAC reader.
f9eed9ab Accumulate multiple modes together in SLAC reader.
0000d4ce Move array reading inside of conditionals.
679d9205 Add ability to open multiple mode files in vtkSLACReader::RequestData.
41bf8621 Change vtkSLACReader::ReadFieldData interface for multiple modes.
efbf5cc0 Make Frequency and Phase internal ivars be vectors.