Adds Slogger2 logging convenience methods to Cordova Plugin template

Logger object is created by TemplateJS and accessible through getLog() method.
Logger sets up 2 slog2 buffers and offers convenience methods to access them from TemplateNDK as easy as 
m_pParent->getLog()->warn("Warning Message");

Also drops extra parts of the sample app, in line with what was done for PreventSleep.