Updating a0poster template

more configuration options
Adding extended version of default beamer template

variables that can be specified:

  - sansfont
  - sansfontscaling (ratio w.r.t. default, eg. 1.2, 1.5, 0.3)
  - mainfont
  - monofont
  - monofontsize (eg. tiny, small, scriptsize, etc)
  - simplenavigation (removes footer and prints just slide number)
  - bullets (replaces triangles by textbullet)
Convening on using 'name' instead of 'names'
Replacing tov.beamer by extended.beamer