[UI] Opening any modal form should auto-focus first field

[egekorkan]

When I want to add a new element, I click on Add Element, then at Thing Description. At this point a window pops up and I need to enter the name of the TD. To do that, I need click with my mouse on the name field. It would be an improvement if this name field becomes automatically active so that typing results on the name field to be changed.

This is valid also for folder and Mashup.

[miguelrk]

This behavior is desired not only for when creating a Thing, but for any modal with a form.

In general: opening any modal form should auto-focus first field.

Addressed by PR #79

[egekorkan]

Fix now on master