General FDSNWS handling on bshm

[marcelobianchi]

Better improve the handling of catalogs from different sources. Probably add the ability for users to configure new sources and they want as long as they are FDSNWS servers without changing the source code.

This includes changes in:

evgrab()
PDENEICEVgrab()
evcatalog()

and probably the creating of a some new methods:

evregistercatalog()
evunregistercatalog()
evlistregistry()