Added more unit tests for IMAP's modified UTF-7 encoder/decoder
Added more unit tests for IMAP's modified UTF-7 encoder/decoder

Tests taken from Daniel D'Agostino's unit tests for his IMAP library

jamie-dainton/MailKit,matt2003/MailKit,sstraus/MailKit,dsbenghe/MailKit,eino-makitalo/MailKit,nachocove/MailKit,mganss/MailKit,jstedfast/MailKit,FubarDevelopment/MailKit,rajeshwarn/MailKit