relax SVN archive

The matrix_angles() function now avoids NaN problems through arccos of numbers > 1.

Added the Saupe element eigenvalues to the align_tensor.display() print out.

Fix for the N-state model when N = 1.

Only add a new tensor object if the tensor doesn't already exist.

Removed a check for the presence of the alignment tensor.

Now align_tensor.init() can be used to reset the tensor values.

Added the method names() to return a list of alignment tensor names.

Large improvements to the align_tensor.display() user function.

Now much more information is provided.

Removed the checks to see if the RDC or PCS data is already loaded.

Now data can be loaded sequentially by a few calls to rdc.read() and pcs.read().

The pcs.read() user function also now accepts the spin_id argument.

Modified return_spin() to handle multiple spin ID strings.