require 'action_view/railtie' for pro compatibility

[MSP-10848](https://jira.tor.rapid7.com/secure/RapidBoard.jspa?rapidView=84&view=detail&selectedIssue=MSP-10848)

Other railties, like jquery-rails, need 'action_view/railtie', but don't
require it themselves, so require it explicitly in
`config/application.rb` to prevent msfconsole boot errors.

# Verification Steps

## msfconsole

### With pro's gems

- [x] `rvm use ruby-1.9.3@metasploit-pro` (or w/e you call your pro gemset)
- [x] `export BUNDLE_GEMFILE=${pro}/GEMFILE` (`${pro}` is the path to your pro repository)
- [x] `msfconsole`
- [x] VERIFY boot without backtraces
- [x] `irb`
- [x] VERIFY `Rails.application.config.action_view` is defined
- [x] VERIFY jquery-rails was loaded `$LOADED_FEATURES.select { |p| p.ends_with? 'jquery/rails/railtie.rb' }`
- [x] `exit`
- [x] `exit`
- [x] `unset BUNDLE_GEMFILE`

### With framework's gems

- [x] `rvm use ruby-1.9.3@metasploit-framework`
- [x] `msfconsole`
- [x] VERIFY boot without backtraces
- [x] `irb`
- [x] VERIFY `Rails.application.config.action_view` is defined
- [x] VERIFY jquery-rails was not loaded `$LOADED_FEATURES.select { |p| p.ends_with? 'jquery/rails/railtie.rb' }.empty?`
- [x] `exit`
- [x] `exit`

## Specs
- [x] `rake spec`
- [x] VERIFY no failures

# Post-merge steps
- [ ] Merge https://github.com/rapid7/metasploit-framework/pull/3578 since it is now unblocked