WIP: Fboemer/inplace ntt

• Fixes #187 (closed)
• Use in-place NTT/invNTT, yielding ~10% performance improvement in NTT
• This should speedup SwitchFormat(), and thereby most HE operations as well.

NTTTransform1024               14.3 us         14.3 us        36699
NTTTransformInPlace1024        11.2 us         11.2 us        62468
INTTTransform1024              11.8 us         11.8 us        59110
INTTTransformInPlace1024       11.1 us         11.1 us        63256
NTTTransform4096               57.2 us         57.2 us        12241
NTTTransformInPlace4096        53.0 us         53.0 us        13194
INTTTransform4096              55.8 us         55.8 us        12607
INTTTransformInPlace4096       51.6 us         51.6 us        13565