Implemented Dynamic Fields feature.

Squashed commit of the following:

commit 3727dc0a5d62e77d168b2e321160a96829bcd524
Merge: 2a5a658 7998ba8
Author: Carlos Rodriguez <carlos.rodriguez@otrs.com>
Date:   Thu Feb 6 14:51:51 2014 -0600

    Merge branch 'master' into noritnk-master-b1

commit 2a5a65853d73ce380e3c8b66d91ba814a95ddaa1
Author: Carlos Rodriguez <carlos.rodriguez@otrs.com>
Date:   Thu Feb 6 14:51:03 2014 -0600

    Implemented small QA fixes.

commit ded8b80711451501209000776b54d2735adc8f21
Author: Norihiro Tanaka <noritnk@kcn.ne.jp>
Date:   Fri Jan 10 23:56:46 2014 +0900

    Fix for some bugs as syntax error.

commit a91024831a5a06ea11df644bcd2823635dfeb89b
Author: Norihiro Tanaka <noritnk@kcn.ne.jp>
Date:   Wed Jan 8 00:23:07 2014 +0900

    Fix for bug which dynamic field isn't used at search.

commit 828730327755a7082c0358606a837923468c2c67
Author: Norihiro Tanaka <noritnk@kcn.ne.jp>
Date:   Sun Jan 5 23:01:05 2014 +0900

    Display and print after selecting a dynamic field as a search attribute.

commit 0c07c93e078b9f12cdbbd048c87384f53773da3c
Author: Norihiro Tanaka <noritnk@kcn.ne.jp>
Date:   Sat Jan 4 17:36:35 2014 +0900

    Resolve cyclic reference between FAQObject and DynamicFieldBackendObject.

commit 764ca494b22fc436713640b138d8a7b331f98055
Author: Norihiro Tanaka <noritnk@kcn.ne.jp>
Date:   Sat Jan 4 09:50:48 2014 +0900

    Some fixes for adding dynamic fields support to FAQ item.

commit cb899026c1b583131ef4b1ebee195c5a7ed600ab
Author: Norihiro Tanaka <noritnk@kcn.ne.jp>
Date:   Mon Dec 16 18:03:19 2013 +0900

    Add dynamic fields support to FAQ item.