Point core-plot submodule to release_1.4
Add core-plot as a submodule
Fix search path again
Point coreplot submodule release-2.0 branch

- The 1.4 release I was using did not have a
  proper gitignore file configured
Removed old core-plot search path

- Fixed linker error caused by
  failing to remove reference to
  old core-plot lib
Merge branch 'igcs-75-coreplot-update'