- ConfigReader is in ApplicationCore.h, but was including ApplicationCore.h itself
- Added include guards to ApplicationCore.h, although it's not stricktly needed (all included headers have one). Might speed up complilation because it makes it easier for the parser.

the swicth because order is not important for these.

ModuleList serves as a container for VariableGroups. The VariableGroups
mirror xml modules in the config file.

ConfigReader: make exception what() message more elaborate when not finding a variable in the config file in get()

configuration variables are now provided to the receivers right away without any read(). Updates will never be sent.

allow obtaining the config values already before connections have been made through a speicial get() function