implemented server-side generic brick architecture

split PostHandler from Brick
added Post class
implemented Wall.post
added support for multiple scripts and stylesheet to Brick
fixed: only set default value for Brick stylesheet if unset
adjusted URL brick to new architecture
implemented client-side generic brick architecture

split PostHandler from Brick
modified ClientUi and DisplayUi to load ClientBricks and DisplayBricks
    respectively
implemented DoPostHandler
removed now obsolete post-new screen
removed now obsolete postSingle property
implemented a screen stack
added post method to ClientUi
ported URL brick (client-side) to new architecture
added maintainer information to bricks
documented brick status concerning new architecture
updated README and default configuration to reflect working bricks
implemented Post.json

also added app to PostHandler and Post constructor
implemented DoPostSingleHandler

also added ui to DoPostHandler constructor
ported Pyng to new brick architecture
added Pyng to default configuration
Merge pull request #50 from NoyaInRain/generic-brick

Generic brick