SelectableRoomHandler: add method to connect two custom participants

Change-Id: I0b26c9ec6dd8a529c5b0ee97eecf90e171acf2b0
selectable.html: add funcionallity to connect two participants

Change-Id: I0377d68cfc7aa1954b360cb3c7863adc628690f0
selectable.hmtl: use buttons instead combobox to select participant

Change-Id: I8e6f9197add651d1d3280fb80cd02d012140c939