[FIX] simplified EmpiricalFormula
[INTERNAL] further cleanup and speed-improvements of EmpiricalFormula
[INTERNAL] made typedef more OpenMS like
[FIX] replaced string conversion by appropriate test
minor fix for lib arch check (removed invalid space in regex)
Merge pull request #988 from timosachsenberg/feature/EmpiricalFormula_refactoring

[FIX,FEATURE,API] simplified EmpiricalFormula