Extensible grammar and runtime

[jfallows]

Note: this requires a backwards incompatible change in the K3PO grammar.
Note: upgrade script provided in tools/upgrade.sed

Added an extensible TypeSystem used by the parser to support custom language elements not present in the core, such as http:method, http:version http:header, and http:status.

accept "http://localhost:8080/path?query"

accepted
connected

read http:method "GET"
read http:version "HTTP/1.1"
read http:header "Host" "localhost:8080"
read http:header "Upgrade" /(?i:websocket)/
read http:header "Connection" /(?i:Upgrade)/
read http:header "Sec-WebSocket-Key" /(?<key>[a-zA-Z0-9+\/=]{24})/
read http:header "Sec-WebSocket-Version" "13"

write http:status "101" "Switching Protocols"
write http:version "HTTP/1.1"
write http:header "Upgrade" "websocket"
write http:header "Connection" "Upgrade"
write http:header "Sec-WebSocket-Accept" ${ws:handshakeHash(key)}
write flush

# connection established

Added an extensible BehaviorSystem used by driver to support runtime enforcement of custom language elements.

New transport schemes can now be implemented outside the K3PO project and be discovered via ServiceLoader by placing the artifact on the <dependency> classpath of the k3po-maven-plugin.

[dpwspoon]

format clean up shouldn't change this

[dpwspoon]

format clean up should not change this comment

[dpwspoon]

It whould be nice to now write:

write http:version "HTTP/1.1"
write http:header "Upgrade" "websocket"
write http:header "Connection" "Upgrade"

as

write http:version "HTTP/1.1"
      http:header "Upgrade" "websocket"
      http:header "Connection" "Upgrade"

Which I don't think is possible as Robot.g is now:

commandNode
      : writeNode		 
      : writeConfigNode

...

writeConfigNode
     : WriteKeyword QualifiedName writeValue*

[dpwspoon]

StructuredTypeInfo needs to

@Override 
public String toString()

as it is called in several Ast*Nodes describe()

[dpwspoon]

Should BehaviorSystem and others (WriteOptionFactory, ReadOptionFactory) be in public API (i.e. not internal packaging). Maybe file a follow-up ticket?

[cmebarrow]

Sed script should not alter any comment lines

[cmebarrow]

@jfallows Since connect and accept uri is now quoted will it allow syntax like

connect "nukleus://streams/{$target}"

that we agreed we'll need for http spec tests?

[jfallows]

The .toString() is now added, the upgrade.sed script now skips "tidying" of comments and has been re-applied to the specification scripts.

The grammar updates for consecutive write http:header (or similar) and "http://localhost:8080/${path}" syntax are both enhancements beyond the scope of this PR which aims to make K3PO extensible.

[jfallows]

Investigating build breakage on Travis.

[jfallows]

Travis build working again.

[jfallows]

Note: we might need some further (minor) changes on stream validation to support custom extensions after write close.

[jfallows]

Note: no need to hold for any changes on stream validation.