add filtering on distance for runningcatalog

This implements feature request #5231

https://support.astron.nl/lofar_issuetracker/issues/5231

summary: 
* adds a filtering option to the running catalog, based on ra, decl and distance (all in degrees)
* A link from a transients page to the filtered running catalog list, with a distance of 0.03 degrees (+/1 100 arcseconds)
* The code is a but ugly at a moment, but it works. With a bit of work it can be added to all list views that are ra and decl based. First I want to know if this is what people want and then i'll try to add it to all list views with coordinates.