relax SVN archive

Large speed ups of the Ln3+ position finding system test.

For for a bug introduced in the last revision (r11314).

The fixed probabilities were not being set for the Ln3+ optimisation case.

Pre-defined probabilities can now be used in the 'fixed' N-state model optimisation.

Fixed the align_tensor.delete() arg unit test to accept None as an arg.

The align_tensor.delete() user function can now be used to remove all tensors simultaneously.

Made a RelaxError less stringent so that the paramagnetic centre can be unfixed.

Added a system test to back-calculated RDCs from a PCS derived alignment tensor.

The RDC and PCS back-calculation user fns now add the alignment ID to the RDC and PCS if absent.

Again this is to allow both data types to be back-calculated in the absence of measured data.

Small fixes and improvements to the rdc.back_calc() user function.

Align IDs are being used instead of RDC IDs so RDCs can be back-calculated even if measured RDCs are
not present. And spin info is also being checked for better error reporting to the user.

The Ln3+ position optimisation system test has been sped up by decreasing the accuracy.