Add explicit error message when interpolating outside of domain

When using spline interpolation with option ext='raise', an error is raised when one tried to interpolate a value outside of the interval defined by the given samples. The error message itself is elusive and not very helpful:

ValueError: Found x value not in the domain

We should catch and re-raise the exception with a more descriptive error message: indicate which input misses validity range (strain, orbits, etc) and how to solve the issue (use longer orbit files).