Dedupe Merge: Option to add email, phone, IM, OpenID information rather than overwrite and inform user of merge behavior for address data

In order to prevent unintentional loss of data AND allow users to merge location-related data into a given location type:
1. On the "main contact" (right side) of the merge screen, when user selects a location type from the drop-down we dynamically display existing data for that location (e.g. address, phone #, email ....).

2. For address blocks - we only support 1 per location type, so if user selects a main-contact location type that currently has address data - we will be overwriting that address data with data from the duplicate contact. We will display "(Overwrite)" next to location type to let the user know this.

3. For phone, email, IM, OpenID - we will always add the data to the existing main contact at the selected location IF the row is checked to merge. We will display "(Add)" to inform the user.

— Original Issue Post ----
currently, the dedupe merge process allows contact information (eg. phone, email, address) from the dupe contact to overwrite existing contact information, or it will be lost when the dupe is erased. however, frequently we do not know which is the most recent or best information, and in many cases both remain valid.

solution: allow duplicate contact information to be *added* (like relationships, memberships, tags, etc.) to the existing contact information. this involves creating new location, if necessary, or just additional phone entries, email, etc. result is that contact info from both original and dupe is kept.