Add ability to parse action url overrides

[Tavio]

The API blueprint specification defines an action as:

Defined by an HTTP request method:

<HTTP request method>

-- or --

Defined by an action name (identifier) followed by an HTTP request method enclosed in square brackets [].

<identifier> [<HTTP request method>]

-- or --

Defined by an action name (identifier) followed by an HTTP request method and URI template enclosed in square brackets [].

<identifier> [<HTTP request method> <URI template>]

The last definition is not currently supported by Drakov as already mentioned in #147. This PR fixes that.

[LKaemmerling]

@marcelogo @yakovkhalinsky is there a way you could review and release this in the next time? We need this really much :)

[kamihouse]

@subinvarghesein

[LKaemmerling]

@marcelogo Sorry for the ping here, but who is responsible for drakov now?