Added newline character between citations and other Extra field content

The current behavior of the plugin breaks the PMID and PMCID variables that are stored in the Extra field. In the Extra field, each new piece of data should be stored on a new line. This pull request adds a newline character between the citations and the other Extra field content. It also includes an algorithm to convert the old format to the new. 

The search behavior is still potentially problematic if other data in the Extra field also includes five digits (e.g., some archive location identifiers). I will submit another pull request that adds a label the citation field to account for this.

The other commits regarding build numbers and builds were only there for my convenience. Please ignore and revert them.