Add support for working with URLs

[oubiwann]

In particular:

• add URL encode function (RFC 3986)
  • [x] support string input
  • [ ] support plist input
  • [ ] support map input
  • [ ] support record input
• add URL decode function (RFC 3986)
  • [ ] support string output
  • [ ] support plist output
  • [ ] support map output
  • [ ] support record output
• add function for generating query string
  • [x] from plist params
  • [x] from map params
  • [x] from URL record
• add function for parsing URL
  • [ ] into plist
  • [ ] into map
  • [x] into record
• [ ] a split function -- like parse, but keeps the params + url together
• [ ] a join function -- like filename:join (both 1 and 2 arity)
• [x] add a URL defrecord supporting the following fields:
  • scheme
  • netloc - this should be another defrecord with the following fields
  • username
  • password
  • host
  • port
  • path
  • params
  • query
  • fragment
• add convenience functions that wrap the record functions:
  • [x] get-scheme
  • [x] get-netloc
  • [x] get-username
  • [x] get-password
  • [x] get-host
  • [x] get-port
  • [x] get-path
  • [x] get-params
  • [x] get-query
  • [x] get-fragment
• add a new constructor that takes a plist and generates
  • [ ] a map
  • [x] a record
  • [ ] a string
• add multi-arity versions of the new constructor
  • [x] takes scheme, netloc, params, query, fragment
  • [x] takes scheme, host, port, path, params, query, fragment
  • [x] takes scheme, username, password, host, port, path, params, query, fragment

[oubiwann]

Need to switch to using yuri for this ...