WIP: Replace bootstrap by purecss.io

[ironjan]

• Fixes #77
• Slims the tool UI down to rasperberry pi compatibility

To Do

• [x] Reimplement/Replace classes: pull-right, nav-pills
• [x] Restyle ausleihe
• [ ] Restyle public (opt.)
• [ ] Restyle admin (opt.)

[ironjan]

.nav-pills li {
  display: inline-block;
  background: red;
}

Needs to be adapted for colors etc. pull-right is probably more complicated.