Reworked object interaction.
Most direct function call between the core, parsers and spellcheckers have been replaced with signal and slot connections. This was done in an attempt to resolve issues with closing
Qt Creator while the plugin is still busy checking a file.
Test were done and the previous crashes that were 100% reproducible could not be reproduced. For now I am assuming that it is an improvement on the plugin. This could also
have solved random crashes that was sometimes experienced when using the plugin.

Project level checking still needs to be done before a new release will be made.