DialogFilter class and DialogHelpers module
Readability improvements (from review) in the dialogs
Reimplementation (and API change) of SystemdJournal::Query
New reorganization

 * Rearranging the resposibilities of some classes
 * DialogQuery becomes QueryPresenter
 * More flexible filtering posibilities in the UI
Remove unneeded SCR import
Merge pull request #1 from ancorgs/code_organization

Reorganizing the code