multiple changes:
* simplify definition components from cpp
* simplify configuration of components
* session and application unlocker lock scope on destruction only if scope was locked before
* move macros to define scoped variables to header tnt/component.h from tnt/ecpp.h to make them
  available in components defined in cpp and construct the key parameter from type and varname
  instead of expecting it as a parameter
* document default components of tntnet from tntnet.so in man page tntnet-defcomp(1)
* use the simplified way to define components in demos
* add include attribute to scope tags