Change the pictogramm of the urbanism plugin

[MaelREBOUX]

We need to change the icon which appears in the side bar. The current is not appropriate.

geor_urbanisme_mapstore/js/extension/plugins/Extension.jsx

Line 106 in 438fd11

icon: <Glyphicon glyph="th-list" />,

After discussion we choose the **fa-university ** one (for the v4.7.0). See : https://fontawesome.com/v4/icon/university
Which is more similar to the orignal one in mapfishapp.