Feature/tao 3145 ck highlight plugin

[krampstudio]

Enables the highlight plugin into the textReader interaction.

Requires oat-sa/tao-core#1001 and oat-sa/extension-tao-itemqti#810

[ssipasseuth]

After updating a pci (either the runtime or creator), you need to register it again in the updater so the new version is registered as the latest one to be used. I have started some documentation here http://forge.taotesting.com/projects/tao/wiki/PCI_development or you can follow the example in this similar PR https://github.com/oat-sa/extension-pcisample/pull/12/files

[ssipasseuth]

The underline style and the new highlight styles are identical. Is it expected ?
I can see also a discrepancy from the AC "EM font color = black"

[krampstudio]

@dietertaotesting took care of the rendered style. In TAO, we have fg=white bg=orange and in invalsi with have fg=black and bg=orange.

Those changes have been merged into develop yesterday.

[ghost]

White contrasts well with orange, black not so much. Invalsi insists on black though - hence the difference