Adds checkSuccess and onFailure methods to poll feeds.

If checkSuccess(val) returns false onFailure is called instead of
onSuccess. If no handler for failures was created onException is called.
Existing entities' behaviour should remain the same. The HttpFeed has a
default success condition of 200 <= responseCode <= 399.

onError is deprecated in favour of onException, to make its purpose clear.
HttpFeed supports authentication

Supply username and password to HttpFeed buider. Uses httpcomponents'
standard mechanisms, so Brooklyn handles everything httpcomponents handles.
Extends HttpService to create servers requiring basic authentication.
Improve distinction between config keys and attributes in JBoss7Server
Enable AS7 management interface security by default

Adds MANAGEMENT_USER and MANAGEMENT_PASSWORD config keys to the AS7
entity. Username defaults to 'brooklyn', password to a random UUID.
AbstractLocation/FixedListMachineLocation: use addChild/removeChild

- was previously overriding addChildLocation
Merge pull request #792 from aledsage/fix/LocationRefactor-subclasses

AbstractLocation/FixedListMachineLocation: use addChild/removeChild
change Location API for clarity on when config is inherited or not
(fixes bug recently introduced somehow where privateKeyFile was not respected for BYON)
CSS: Solved too-many-scrollbars on add application modal dialog.
Merge branch 'master' into misc
CSS: Scrollbars to 'auto' by default.
CSS: Solved occassional jiggldy-pigglty layout of lozenges in add application dialog when using Chrome.
CSS: Repositioned Application Content navigation tabs.
CSS: Solved add applicaiton location select dropdown too small on FireFox.
CSS: Increased minimum size of the JSON textarea in the application explorer.
CSS: Added margin below swagger ui content.
tweak timings to make thread/timing tests more robust (in response to CloudBees failure)
CSS: Nav colour not actually '!important' here. Will prevent problems later.
CSS: Add Apllication Search box spacing improvement.
CSS: Swithced to min-height to give sufficient field size in FF (Add Application Configuration).
Set NginxController SERVICE_UP feed to accept any HTTP response