Added fixed_vector class and relative reg. tests
Added fixed_matrix class and relative unit tests. Altered abunch of items to avoid warnings in clang. Moved the specialization of std::complex in deduction to avoid clang errors. Corrected a potential bug in assignment.hpp with respect to static relative moves.
Merge branch 'feature/ublas00002_fixed_matrix' into ublas_develop
Minor changes in doxygen doc