add a intro + readmore component

[tttp]

new component like the eci one:

• display the top of the text + button "readmore" to see the full text

should be configurable via the portal, similar as TTag, but (to be confirmed) an additional param or two:

• number of paragraph to display before the "readmore"
• other key to display as intro

[tttp]

done

you can either insert it like a normal portal (with a selector) or put it on the left hand column
how to use :

"portal": [
{
"column": "left",
"component": "TTag",
"message": "campaign:guideline"
},
{
"column": "left",
"component": "ReadMore",
"length": 2,
"message": "campaign:letter"
}
]