Bug 879511 - [email/IMAP] date-time parsing regex does not accept legal "SP DIGIT" syntax

also removes speculative parseImapDate logic function that is not used.
Merge pull request #217 from asutherland/imap-date-time

Bug 879511 - [email/IMAP] date-time parsing regex does not accept legal "SP DIGIT" syntax. r=lightsofapollo
Bug 860262 - [Email] When selecting the option “replying to all” or “reply” or “forward” on an email that was previously sent without Subject, the new Subject is shown as: “Re:null” or “Fwd:null”
Merge pull request #219 from mozshiao9/master_email_860262

Bug 860262 - [Email] When selecting the option “replying to all” or “rep...