Add AGS global solver (#194)

Add AGS global solver  (#194)

* Rely on ciso646 and __cplusplus macro when detecting cxx

* Add CXX11 flag to cmake

* Add a stub for AGS algrithm

* Finish basic integration of AGS

* Clenup ags header, change cmake for test

* AGS: add stop by reaching required value

* AGS: add stop by timer

* AGS: add correct return code for max_time stop

* AGS: stop instead of throwing an exception

* Get rid of unused code

* AGS: use NLOPT_CXX11 macro

* AGS: updated documentation

* AGS: fix wrong ifdef

* AGS: use spaces rather than tabs

* AGS: fix enum name

* AGS: fix wrong calculation of constraints

* AGS: add an example of problem with nonlinear constraints

* AGS: update docs

* Fix minor issues

* AGS: allow up to 10 dimenstions instead of 5

* AGS: fix warnings

* AGS: fix zero evaluations counter, set default maxeval

* AGS: fix generation of test suite