Add apache URL encoder

See #504 .

* update guava to have access to UrlEscapers
* add function in morph to encode item
* add morph function description
* add schemata used to include morph function
* update test file
Good point: the name is a relict of my first try of the implementation using the apache urlencoder (which didn't do the job right so I switched to guava). Will use `urlescape` as you propose. Generally: yes, this files are all needed because it'is the first custom morph function in lodmill-rd. We have once implemented this is the oer/worldmap branch, though , see  https://github.com/hbz/oerworldmap/commit/1e255504b0ec9f260e1cd3188854a47c81e2fc18. I think this urlescape should be the standard in metafacture instead of their use of java.net.URLEncoder , but for the moment it's easier to change it this way.