Fix the tree branch stylesheet selector

Tree branch stylesheet should only apply to the session tree,
not to the shortcuts settings tree and so on.
Cleanup and make CommandParser fully static non-QObject
Restore aliases wizard page
Restore Settings::aliases
Add basic AliasManager
Include aliases to command completion
AliasesWizard: remove the edit button
AliasesWizard: remove icon per row
AliasesWizard: remove the remove-button
AliasesWizardPage::addRow()
AliasesWizardPage: ignore empty aliases/commands