add dependencies on pkgconf
fixes and enhances hasse_invariant and hasse_invaraint__OMeara

Improves functions to compute hasse invaraints over number fields, adding the necessary documentation, and also fixes an error in indexing from the current code.
updated examples from last commit

In the previous commit the docstrings used a function which is not yet implemented in sage.
Removed trailing whitespace from last commit
Reverted one example in doctest

Instead of changing both doctests to [1,-1,5] I changed the doctest of hasse_invaraint__OMeara back to [1,-1,-1]
Reverts one doctest to old example, ignore last commit

Previous commit was not checked for accuracy, this should be correct now.
Trac #16368: Missing pkgconf dependencies

We should build the pkgconf package before anything that uses pkg-
config.

URL: http://trac.sagemath.org/16368
Reported by: stephen
Ticket author(s): Volker Braun
Reviewer(s): Martin Albrecht
Trac #16379: Compute Hasse invariant over number fields and fix current implementation

This patch will enhance the current functions hasse_invariant and
hasse_invariant_OMeara to include computations of Hasse invariant for
quadratic forms over number fields.  In addition, this patch fixes an
indexing error in the original hasse_invariant_OMeara code, which
currently reads
{{{
for j in range(n-1):
    for k in range(j, n):
}}}
but should read
{{{
for j in range(n):
    for k in range(j, n):
}}}
to be consistent with OMeara's algorithm.

URL: http://trac.sagemath.org/16379
Reported by: annahaensch
Ticket author(s): Anna Haensch
Reviewer(s): Peter Bruin