Synthesis, Crystal Structure, and Properties of Aquacopper(II) N‐[(1‐Methylimidazole‐2‐yl)‐methylene]‐β‐alaninate Hexafluorophosphate and Copper(II) N‐[(1‐Methylimidazole‐2‐yl)methyl]‐β‐alaninate Perchlorate