Provide ability to search/distinguish "primary" membership entity

Membership types can be defined with a relationship such that related contacts inherit the parent membership. This is done by creating a replicate membership record for each related contact, with a value in the civicrm_membership.owner_membership_id field to designate the parent owner.

There currently is no way to distinguish the parent from the child memberships in the search interfaces, a critical function as most organizations likely measure their membership based on the "primary" member, not the related child members.

Find Members, Advanced Search and Membership Tab
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Add radio button to to CiviMember > Find and Advanced Search > Membership forms (above Find Pay Later checkbox).
[ ] All Members [ ] Primary Members Only [ ] Related Members Only

Add link to "View Primary" member in the Find Members search results listing (for "child members").

Add link to "View Primary" member in the contact Membership tab (for "child members").

Add "(by relationship)" flag below Membership Type in both selectors.

View Member
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Add link to view Primary member contact record (for "child members").

Removed Edit and Delete links when viewing a child member (since there operations are not allowed).

Modified MembershipView.php to allow direct linking to View Member page w/o going through Tab.php (this allows us to use URLs like this: civicrm/membership/view?id=NN) and bypasses a large number of unneeded queries. I've filed an issue for 3.2 to impement this
refactoring for similar "view" pages (Contribution, Participant, Pledge): http://issues.civicrm.org/jira/browse/CRM-5230

Export Members
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"Primary Member ID" (owner_membership_id) was already part of default "Export Members" - but the title was not set properly. I've fixed this.

Including "Primary Member" (display_name) in default export is out of scope for this release. I've filed an issue for 3.2: http://issues.civicrm.org/jira/browse/CRM-5231