gnu: Reword and extend descriptions for some KDE packages.

gnu: Reword and extend descriptions for some KDE packages.

* gnu/packages/kde-multimedia.scm (libkcompatdisc)[description]: Extend.
* gnu/packages/kde-pim.scm (akonadi-search, kalarmcal, kdemailimporter,
  kdepim-apps-libs, kidentitymanagement, kldap, kmailtransport, kmbox, kmime,
  kontactinterface, kpimtextedit)[description]: Reword and extend.
  (ktnef, kpimcommon, libkdepim)[synopsis, description]: Reword and extend.
  (kmailtransport)[synopsis]: Fix space.
* gnu/packages/kde-systemtools.scm (khelpcenter)[description]: Extend.