fix: STORE for iCloud and other strict IMAP servers (master branch)

[miaulalala]

Apple's iCloud IMAP server (and possibly others, although I haven't tested it) want brackets around any FLAG command params as shown in the examples of RFC3501.

If the brackets aren't added, the command fails with BAD Parse Error for the \Delete FLAG.

To fix this, wrap the params of a STORE command in a Horde_Imap_Client_Data_Format_List.

Otherwise, the \Delete FLAG, \Seen FLAG and possibly all other PERMFLAGs aren't added, even if the STORE command doesn't return a BAD response.

[what-the-diff]

PR Summary

• Modification in lib/Horde/Imap/Client/Socket.php
  The way this program defines certain options has been altered. Now, instead of the old method, it uses a more advanced feature for defining these attributes. This modification is expected to improve both the effectiveness and performance of the program.

[ralflang]

@mrubinsk You must decide if this is fit for master. For FRAMEWORK_6_0 I am running with it (see #31 )