Allow different keyboard shortcuts and interface custom configuration by workbench

[SrNetoChan]

Depending on the workbench, we may want the same keyboard shortcut for different things. Would be nice if the workbench could save the keyboard shortcuts configuration. Same goes to custom interface configuration, where you can hide certain buttons and tools from the interface.

[s-m-e]

I explored this a while ago, there were some limitations within QGIS preventing this from working properly. I'll check again though.