Fixes #5236 - Speed up content view publish

Sped up indexing content for a RHEL content view from 20 min to 30-40 seconds.
fixes #5183 - Rename Systems to Content Hosts throughout the UI
Fixes #5243 - Store the content view next version

When destroying content view versions, we were keep track of the last version
number so we'd publish using version numbers that were deleted. With this
change, we'll store the next version number, increment it, and use it for new
versions.
Merge pull request #3984 from bbuckingham/system-ui-rename

fixes #5183 - UI - Rename 'System' to 'Content Host'
fixes #5233 - System Groups UI - fix cross-linking to the systems page

The cross-linking is using the active record id; however, the systems
page expects the system uuid to be used.
fixes #5232 - System Groups UI - fix link from system count to the group's System list.

Minor change so that clicking on the system count from the System Groups
list will take the user to the group's System list.
Merge pull request #3993 from bbuckingham/fixes-5232

fixes #5232 - System Groups UI - fix link from system count to the group's System list.
Merge pull request #3992 from bbuckingham/fixes-5233

fixes 5233 - System Groups UI - fix cross-linking to the systems page
Merge pull request #3989 from daviddavis/temp/20140417122656

Fixes #5236 - Speed up content view publish
Merge pull request #3991 from daviddavis/temp/20140418085641

Fixes #5243 - Store the content view next version
Fixes #5255 - Version destroy plan takes 20+ minutes

Removing before_destroy hook and package orphan code from clear_packages_index.