Added settings class and initialise it in git_dashboard_init

Settings class contains most common functions, more will follow.
Project file was not saved
Changed compiler settings

Added -O3 for speed optimization, -Wmain for main-errors, -pedantic for
strict errors and -std=c++11 to comply with the newest specs.
Completed Settings class

Including GError and gsize
Merged 'settings' into 'master'