[#1792] Add filters UI to filterable resource view's manage page

Most of the code was extracted from ckanext-basiccharts and
ckanext-viewhelpers.
[#1792] Move Object.keys() polyfill to its own file

We need it on more than one module, so we move it to its own file and always
load it when IE <= 8, so the other JS files can rely on Object.keys() being
available.