Merge pull request #614 from peastman/master

Fixed a compilation error in double precision mode
Merge pull request #615 from peastman/master

Switched to a slightly faster (and more accurate) approximation for erfc()
Updated code to obey BUILD_TESTING to allow for disabling of test compilation
Merge pull request #617 from Omegaice/master

Updated code to obey BUILD_TESTING to allow for disabling of test compilation
Preliminary implementation of JIT compilation for CompiledExpressions
Update AmoebaMultipoleForceImpl.cpp

@rmcgibbo and @mpharrigan convinced me I should have just fixed it myself.
JIT compilation uses optimized calculations for many of the most common operations
Added more optimized operations to JIT compilation
Added #ifdefs and CMake logic for deciding when to use JIT
Fixed compilation error on Linux
Update AmoebaMultipoleForceImpl.h

typo fix
Update AmoebaMultipoleForce.cpp

typo fix
Update AmoebaMultipoleForce.h

typo fix
Update amoebaKernels.h

typo fix
Update AmoebaReferenceKernels.h

typo fix
Merge pull request #619 from schwancr/patch-1

Update AmoebaMultipoleForceImpl.cpp
Merge pull request #620 from peastman/master

AMOEBA uses fast approximation for erfc()
Fix issue where the last CMAP defined in a parameter file is not added to the
parameter set.
Fix comments.
Merge pull request #621 from swails/charmmparameter_fix

Fix issue where the last CMAP defined in a parameter file is not added to the parameter set.