Remove deprecated event handler methods from extensions

[Nicklas Nordborg]

Lots of extension points define properties such as 'onclick', etc. which point to a javascript snippet to be executed when the (click) action occurs. This style of programming has been discouraged since BASE 3.3 (see #1730).

I think it is time to make the final switch and remove support from the BASE core for inline event handlers. Extension developers should have plenty of time to fix their extensions.

[Nicklas Nordborg]

(In [6652]) References #1813: Remove deprecated event handler methods from extensions

Fixed for actions and taglibs related to menu items.

[Nicklas Nordborg]

(In [6653]) References #1813: Remove deprecated event handler methods from extensions

Fixed for actions and taglibs related to tab controls.

[Nicklas Nordborg]

(In [6654]) References #1813: Remove deprecated event handler methods from extensions

Fixed for actions and taglibs related to buttons and icons.

[Nicklas Nordborg]

(In [6655]) References #1813: Remove deprecated event handler methods from extensions

Fixed for other actions and taglibs.

[Nicklas Nordborg]

(In [6658]) References #1813: Remove deprecated event handler methods from extensions

main.js has been deleted.

[Nicklas Nordborg]

(In [6812]) References #1813: Remove deprecated event handler methods from extensions

Trying to remove code examples that use inline javascript event handlers.