Chaining shared addresses doesn't work correctly

With versions 4.7.24 and older, you can create a chain while sharing addresses. Changing the head of the chain only changes the addresses 2nd in line. Proposed fix: Prevent chaining addresses ad infinitum, and prevent sharing an address with itself. When changing a shared address, change the sharing too.

Example 1 using an address from a contact that uses a shared address Steps to reproduce: 1. First, create three contacts: A, B, and C 2. Create an address for contact A 3. Use contact A's address for contact B 4. Use contact B's address for contact C 5. Change contact A's address Result: Contact C's address is not changed Example 2 using an shared address for a contact that shares its address Steps to reproduce: 1. First, create three contacts: A, B, and C 2. Create an address for contact A 3. Create a different address for contact B 4. Use contact A's address for contact C 5. Use contact B's address for contact A 6. Change contact B's address Result: Contact C's address is changed at step 5, but not at step 6, because contact C uses contact A's address Example 3 sharing an address with itself 1. First, create a contact: A 2. Create an address for contact A 3. Use contact A's address for contact A's address Result: Share succeeds, and an endless loop is created

Example 1 Using contact B's address for contact A changes its own address AND contact C's address Example 2 Contact C uses contact B's address, changing contact B's address changes contact C's address Example 3 Share fails with with a warning message