* Use locale independent conversion from double to string

boost::lexical_cast<std::string>(0.1) returns "0,1" on Dutch, German and probably some other locales
which boost::lexical_cast<double> fails to parse even on Dutch, German etc locales

so this commit uses std::ostringstream which seems to be the only sane way to ignore locale

* clang format

* use std::locale::classic() instead of std::locale()

std::locale() copies the global locale, which is already used at construction time of std::stringstream. So this was a noop.
The global locale defaults to std::locale::classic() but it might have been set somewhere else before,
 so explicitly setting std::locale::classic() makes this code independent of locale settings elsewhere.

* factor out conversion from double/float to string into moveit_utils

* clang format

* more explicit description

Co-Authored-By: simonschmeisser <s.schmeisser@gmx.net>

* adress documentation comments

* add and use conversion functions from string to double

* Don't write localized doubles to benchmark results

* use template internally to avoid code duplication

* Add error handling for std::string->float/double

now throws a std::runtime_exception if errors occur.
For planners this gets caught in planning_pipeline::PlanningPipeline::generatePlan
and there are no further users of toDouble/toFloat currently

* remove extra parantheses again

* Code review comments by Dave