Improved Lapack interface

Description

Improve the Lapack interface and fix several problems and potential bugs:

• The routines that destroy matrices not have a flag to preserve them. This flag is mandatory.
• The least_square routine is now implemented for the complex case. This fixes a bug for DIIS mixing with complex numbers.
• The interface for the routines dsyevx and zheevx was not correct. They are not used at the moment.
• Adding some missing intents
• Refactoring of some real/complex versions of Lapack routines.

Closes #313 (closed)

News snippet

Improve the Lapack interface and fix several problems and potential bugs.

Checklist

• I have checked that my code follows the Octopus coding standards
• I have added tests for all the new features added in this request.