Optimization: avoid duplicate creation of T*CheckBoxList, T*RadioButtonList js items
Added some TCallbackClientScript demos

cherry-picked from 781f6731122cf622bcdf64441d247b5e37a2c3d0
Deleted old PEAR-based buildscripts upgrader
Avoid dependency loop between TRadioButton and TRadioButtonList
prado-cli: don't add php's terminator tag to generated files
Removed ?> from buildscripts and demos
Removed ?> from tests
Big quickstart doc overhaul, pt. 1
Quickstart Doc overhaul, pt. 2: active controls + minor fixes
Dropped Markdown for Parsedown
Added quickstart doc for TMarkdown