Create .gitignore

Ignored files:
.gitignore
semg_mkl15z128vlh4/.settings/
semg_mkl15z128vlh4/Documentation
semg_mkl15z128vlh4/FLASH
semg_mkl15z128vlh4/Project_Headers
semg_mkl15z128vlh4/Project_Settings
semg_mkl15z128vlh4/.cwGeneratedFileSetLog
semg_mkl15z128vlh4/ReferencedRSESystems.xml
semg_mkl15z128vlh4/SaAnalysispointsManager.apconfig
semg_mkl15z128vlh4/*.traceConfig