[Thermo] Check composition strings for invalid float literals

git-svn-id: https://cantera.googlecode.com/svn/cantera/trunk@2866 02a645c2-efd0-11dd-984d-ab748d24aa7e
fpValueCheck detects (invalid) decimal ponts in exponents

git-svn-id: https://cantera.googlecode.com/svn/cantera/trunk@2867 02a645c2-efd0-11dd-984d-ab748d24aa7e
Deprecate unused stringUtils functions

git-svn-id: https://cantera.googlecode.com/svn/cantera/trunk@2868 02a645c2-efd0-11dd-984d-ab748d24aa7e