Rework path builder to support more functions

[magodo]

The body pattern (i.e. body or body.x) now can add a chain of functions (applied from left to right), in form of $f1.f2(body.x).

Supported functions include:

• escape: URL path escape (by default applied)
• unescape: URL path unescape
• base: filepath base
• url_path: path segment of a URL
• trim_path: trim path

Removes the previous #(...) pattern, instead use url_path.

Fix #105

[hongkongkiwi]

Very nice! This provider is really flexible I love it.

Thank you for putting the time in to make it.