fix (directiveCompiler): change pattern to look for when checking that template contains one root
refactor (buMain): remove bu$Directive class as well as bu$directives service

BREAKING CHANGE
feat (bu$directives): add directive registry with requirement management
feat (bu$directiveCompiler): add ability for pre- and post-links to be injected
feat (bu$directiveCompiler): call pre- and post-links with their respective injectors
feat (bu$directiveCompiler): add a more complex directive lookup
feat (bu$storage): add storage factory which could be used for adding expando objects to DOM elements
feat (bu$require): add a requirement controller lookup which can be injected into linking phase
fix (bu$directiveCompiler): fix masking so that linking functions see the scope one tick after the initial state
add (BootstrapUI): add augmented service BootstrapUI which gathers all the essentials
feat (BootstrapUI): add ability to add directives en mass
chore (buMain): put utility functions in their own block
fix (BootstrapUI): make BootstrapUI a provider so that it is injectable into providers as well

The two demo directives <hello-jumbo/> and <learn-more/> are also now adapting the new system wherein calling the $injector is unnecessary.
fix (bu$directiveCompiler): add support for resolve methods
chore (directives): adapt directives to new style of dependency polling
fix (bu$directiveCompiler): change injector instance for directive factories to one that enlists services
chore (bu$directiveCompiler): remove references to $injector in factory dependencies
fix (bu$directiveCompiler): return the descriptor from the `defaults` masker
test (bu$directiveCompiler): resolve test failures