Temporarily remove storage and load of Euler databases in ELLFF.

In Sage 5.7 ZODB was removed and so an alternative is needed.  Until this is provided, we remove support for databases.
added condiiton to make sure we only use the real-parameter Bessel funciton in the correct range
Added Bessel function for real parameter from SciPy in order to compute exceptional eigenvalues. I decided to do this because debugging my own routine bewcame tedious...
added some debugging printouts
fixed bug
(Hopefully) Fixed several bugs with respect to the coordinate system used.
There was a bug reported by Sven Möller that caused _action_of_Gamma0 to fail
because this method still used the old ._L list of elements in WeilModuleElement.
However, there werde quite a few bugs regarding the use of the el_index etc. - methods.
This is all due to the fact that can_coords=True has to be used
when the generators and their orders are used for the coordinate functions.
I think this should be changed to using the elementary divisors instead.
But for now, I just fixed the bugs (ugly...)

Conflicts:
	psage/modules/weil_module.py
Fixed bug when called by Sage matrix instead of SL2Z element
changed debugging output
Merge remote-tracking branch 'stephan/weil_module_bugfixing'
Added some documentation and fixed random_element and the test_formula function
Added a reimplementation of an_element() since the default function used multiplicative instead of additive group
Changed the identity in SL2Z to SL2Z.one() to avoid a strange error
Merge pull request #3 from martinra/ellff_db

This is to make PSage run with 5.7
added a more general eta quotient multiplier
changed a comment
Merge branch 'master' of github.com:fredstro/psage
added funcitons for plotting Maassforms
removed import of functions no longer in sage
working on refinig the plot
Merge remote-tracking branch 'upstream/master'