Show the same right-click context menu functionality for entities and components in Scene Structure and EC Editor windows

[Stinkfist0]

Basically do same what was done for asset items recently https://github.com/realXtend/naali/issues/399?source=cc

[jonnenauha]

Some thoughts on the UI for whoever might implement this:

• When you right click on component Save <component_name_ec_prefix_removed>.. should only save a txml that has that component. Just like it does to clipboard when you do Ctrl+C. When you right click the empty background of EC Editor it should say Save Entity... and store the whole entity.
• If not too much trouble I'd like to see a Import Components... option after to Save entity... It should only accept txml files that only have components in it (created by Save <component>.. item earlier, not ones with entities.
• I'm really missing the Functions and Actions from the Scene Struct window when you click on a component. This is a big pain in the ass to open the scene struct, find the entity you have selected in the EC editor, expand it and right click on the component!

Make the functions popup dialog look nicer via stylesheets, make similar to the other EC editor popup windows, change window flags to Qt::Tool. Check if the generated UI for setting function call params could be made more clear to the user. Also check for bugs as @Stinkfist0 noticed today that sometimes not all widgets get on screen (eg. select a func that only takes a bool).