Add function "Gaussian" and others

Add function "Gaussian".
Add compiling scripts for Linux. (Thanks msg7086)
Use float instead of double to increase speed.
Fix Gaussian range LUT generation to get equal result for all bit depth.
Remove unnecessary VapourSynth interface function prototypes in head
file.
Some cosmetics.
Add new algorithm for Bilateral

Bilateral: Add new Bilateral algorithm with truncated spatial window and
sub-sampling, which is more suitable and faster for small sigmaS and
small sigmaR.
Bilateral: New parameter "int[] algorithm", when set to 0, it will
select appropriate algorithm according to sigmaS, sigmaR and PBFICnum.
Use aligned_malloc instead of new for image buff.
Default parameters were changed.
Destructor and some member functions were added to Data class, for
neater and safer code in VapourSynth interface.
Create README.md
Update README.md
Update README.md
Cosmetics

Remove VapourSynth headers from project.
Numeric.h renamed to Helper.h.
Correct some warnings and compile problems