fix add nested resource in has_many form builder
Added cucumeber scenario for belongs_to when optional
Refactored Namespace to store a collection of menus
Major refactoring of Menu system to support multiple menus
Added DSL method for switching global nav menus
Added documentation for belongs to
Fixed issue with new menus and the root namespace
Using sass ie-hex-str for colors in IE filters

This fixes blue buttons (#1252) issue in IE, tested in IE9.
JS cleanup, dynamic datepickers, and slim filter queries

+ evaluate dynamically added datepickers (f.has_many form)
+ Filter form: don't pollute the URL bar with empty input values
+ Clear Filters button: remove return value (it's never reached)
Added ability to add custom menu items
Menu item URL is now instance_exec'd in the view

This gives us access to all the rails URL helpers when defining routes
in the initializer.
Make sure assets are precompiled on Heroku

Heroku recommends that `config.assets.initialize_on_precompile = false`,
which means that this initializer will not be invoked by
`rake assets:precompile`, which forces developers deploying to Heroku
to duplicate this initializer in their apps' configs.
Menu system accepts block to defer until runtime
UtlityNavigation removed, uses menu system

* MenuItem#label now accepts a proc evaluated in view context
* MenuItem#dom_id of '#' is now dispalyed instead of hidden
* DSL#display_menu now DSL#navigation_menu
* Docs updated on how to override utility nav
Adjusted Spanish locale using gender-neutral expressions to avoid the use of (a).
Changed "resetear" to "restablecer" and "exitosamente" to "con éxito".
Tweaks suggested by @Daxter
Merge pull request #1967 from reverbhq/menu-updates
Merge pull request #1973 from laffinkippah/master

Adjusted Spanish locale using gender-neutral expressions and other minor tweaks.
Adds the ability to use starts_with and ends_with in string filters

filter :title_starts_with, :as => :string
filter :title_ends_with, :as => :string

https://github.com/gregbell/active_admin/issues/1958
Merge pull request #1962 from howaboutwe/1958_allow_filtering_with_starts_with