Remove ActViewFileNewTab
remove ActViewFile
Remove treeView_doubleClicked

TreeView no longer exists
Remove openFileTab
remove FileView
Merge branch 'remove_fileview'
Remove TAB_REV
Remove FileContent
Remove Annotate
Remove FileList
Remove Domain::setTabCaption
Remove tab_remove
Remove MainImpl::eventFilter

Seems to be responsible for switching through the tabs with your mouse wheel while pressing Alt. No longer needed, so we can remove it.
Simplify MainImpl::currentTabType
Remove unused MainImpl::firstTab
Remove unused MainImpl::getTabs
Remove unnecessary MainImpl::tabWdg_currentChanged
replace TabWidget with a StackedWidget
Merge branch 'use_stackview'
add a QTreeWidget as future navigator to main window