Fix PHP 5.4 fatal error

Drush is telling me Fatal error: Call-time
pass-by-reference
Merge pull request #360 from illmasterc/php-5.4-compatability

Fix PHP 5.4 fatal error
Improve wording in not currently available dsm
Add js to show/hide become available

Only show become avaiable calendar if not
currently available is checked

Issue #333
Improve presentation of becomeavailable Issue #333

This is @illmaasterc's commit moved back in.

Move field up to below the parent
  "not currently available"
Use date-popup field type

Issue #333