Refactor find-data dialog.

This commit refactors find data dialog to resolve several bugs as well as
similify the code. Now pqFindDataDialog relies on using separate classes for
each of the different components in the dialog making is easier to manage
responsibilities between the various components. Also resolves BUG #14317 and
BUG #14285.

This removes obsolete classes like pqSelectionInspectorPanel, pqQueryDialog and
their UI files as well.

Additionally, this commit fixes pqProxyWidgetDialog to use a container to avoid
proxy widgets not being spaced correctly.

Change-Id: Id51c9f9eceed314f2e9d9823e0523cc1d6037c06
Merge topic 'fix_find_data_dialog' into next

a1bf4a7 Refactor find-data dialog.