Add possibility to get URL parameter value as a list of string

In PHP world, it is able to get a URL parameter value as a list of string using a special syntax: param_name[]

Ex: foo[]=1&foo=2&foo[]=3

request_get('foo') => array('1', '2', '3')

In Java/Servlet world, it is able to get a URL parameter value as a list of string using a trivial syntax without square bracket: param_name=1&param_name=2

Ex: foo=1&foo=2&foo=3

Request.getParameter('foo') => ArrayList('1', '2', '3')

It is great if Bottle can support both syntax (both syntax can be mixed together).

+ request.params.get('foo') returns the last value in URL: 3
+ request.params.getall('foo') returns all values as a list: [1, 2, 3]