account.plist used to specify mail account data

Instead of hardcoding it. Excluded from the repository via .gitignore. Also adding TestData to the project, compiled into the Test bundle.

Pushing the iOS deployment target down to 4.3, and ensuring that all projects have the same value there.
Fixing Core Folder tests

sentDateGMT has been removed, changing to senderDate. Also, changing from bodyPreferringPlainText to just body - the former required an out parameter that was not being provided.
MIME/CoreAttachment tests get files from bundle

Because in the newest simulators, your current working directory is more like it is in when you're on the phone itself.

Also no need for the filePrefix var any longer.
Core Message tests: files in bundle, testSentDate

testSentDate wasn't quite passing: sentDateGMT has been removed and the number of seconds representing the date the email was sent is not what was there before. Fixed.

Also, we needed to pull the message files out of the test bundle.
Core Message tests whitespace
Fix to Core Folder tests; senderDate returns nil

Noticed that this change was necessary to get all Core Folder tests passing. Those tests expected senderDate to return nil if there was no message loaded.
Properly pulling MIMETests/testBruteForce files
CTCoreMessage.htmlBody now behaves like .body

It calls fetchBodyStructure if myFields or myParsedMIME is null, just like .body does. Two new tests added; the change to htmlBody is required to get them both to pass.
Merge pull request #67 from NiKnight/master

Fixes to MailCore tests; no hard-coding of mail account data, proper test data file access