Add an include for std::accumulate.

Refs #7229
Added extensions to test files so they can be found.

Refs #7229
Tie all the properties to their widgets.

This make the whole thing less error-prone and gives me a list of
all the property widgets.

Refs #7229
Unified the code for handling Browse buttons.

Will be easier to add another one now.

Refs #7229
Added DTC widgets to the UI.

Refs #7229
Code for connecting DTC widgets to algorithm properties.

Refs #7229
Deal with the situation when ws doesn't contain any auto-grouping info.

Plus improve other error messages.

Refs #7229