Add more checks for decomps provided by user

[jayeshkrishna]

Add more checks on the decompositions provided by the user

• Check for -ve values in the decomposition
• Check if the values are monotonically increasing

Since some of these checks are costly we should also consider adding a "DEBUG " or "EXTRA_CHECK" mode where we perform more costly user argument checking etc. As part of this issue we could move any current user arg checks that are costly under this mode.