Maintain hostgroup selection after assign host

This patch updates the deployment show page to maintain the selected
HostGroup after a the user selects the "Assign / Unassign" button.
Previous behaviour reset the selected Hostgroup to the first Hostgroup
listed.
Merge pull request #126 from mtaylor/hostgroup_selection

Maintain hostgroup selection after assign host
Add weights to provisioning and configuration actions

so a host is no longer showing as 50% done just after reboot
Merge pull request #127 from pitr-ch/master

Add weights to provisioning and configuration actions
Added import/export functionality for deployments

This commit makes it much easier to reproduce deployments based on prior ones.

Deployment export is based on the deployment summary page, but output format
is yml, and internal IDs are removed, in favor of puppetclass names and Staypuft::Role
names, in order to ensure that the format is portable across deployments and
across foreman instances (assuming Role/puppetclass names are the same).

Import pulls a previously exported deployment param set into an existing deployment object.

This may not be ready to merge yet. Two remaining categories of work:
1) styling -- the 'import' form on the show page may need extra styling
2) validation -- this has not yet been tested for various edge cases
   (i.e. invalid yml input, missing and/or extra params, roles, etc.)