Catch cases where CASTEP recovers from LAPACK error

[zhubonan]

The plugin detects the err files in the calculation folder and consider the calculation to be failed if they exist.
However, an err file may still be there is CASTEP detected an error but recovered it itself.
In this case, the calculation should not be treated as failed.

Example content of the file:

Warning, Castep has detected a problem with your maths libraries (LAPACK).
Attempting to work around the problem...
(Information for developers: zheevr diagonalisation error  0.727E-02; zheev error -0.247E-13; Hermitian error:  0.684E-15)
Work-around was successful, continuing with calculation.