Changed version and changelog for hotfix

CHANGELOG

+BornAgain-1.5.1, released 2016.02.18
+Hotfix:
+  * Bug #1341: GUI crashes if simulating with 1D lattice interference function
+  * Bug #1338: Crash while saving certain project file
+
 BornAgain-1.5.0, released 2016.02.15
   > API changes
     1) FTDecayFunctions introduced to use together with lattices (setDecayFunction)

VERSION.cmake

 set(BornAgain_VERSION_MAJOR 1)
 set(BornAgain_VERSION_MINOR 5)
-set(BornAgain_VERSION_PATCH 0)
+set(BornAgain_VERSION_PATCH 1)