Moved class 'Extensions' up hierarchy, from project i18n.MVC3 to i18n, thus allowing it to be used from i18n.
fix for problem with multiple-line strings of 1 char not reading. Involved replacement of Regex with string extension helper for unquoting strings. The following PO now parses correctly:

msgid "A"
msgstr ""
"A"
""
"B"
"CD"

This parses to "ABCD".
Added handling of escaped characters in PO msgid and msgstr strings. E.g. if the msgstr value is itself to be a quoted string such as "Hello", this was being loaded as \"Hello\". Now loaded as "Hello".
Improved handling of a race condition.
performance improvement: replaced list<msg> with dictionary<msgid, msg> for faster lookups.