Add audit symbol component.

src/app/dars/audit-legend/audit-legend.component.html

src/app/dars/audit-legend/audit-legend.component.scss

src/app/dars/audit-legend/audit-legend.component.ts

src/app/dars/audit-symbol/audit-symbol.component.html

src/app/dars/audit-symbol/audit-symbol.component.scss

src/app/dars/audit-symbol/audit-symbol.component.ts

src/app/dars/audit/audit.component.html

src/app/dars/audit/audit.component.scss

src/app/dars/dars.module.ts

src/app/dars/models/audit-symbols.ts

src/app/dars/pipes/requirement-symbols.pipe.ts