Major changes:

79b9123@Fall back to the linear FDR estimation approach when fuse_count < decoy_count. This change will affect the results a lot in some cases.
58b5a76@Support more enzymes.
62947bb@Support up to two enzymes simultaneously.
af07e84@Add running time to logger and minor improvement.
40d33b2@Delete q-value column in the decoy output to avoid a confusion.
3c8f9fd@One more database_type in the parameter.
c4f5bd0@Output some warnings regarding the "not enough data points" issue.

Minor changes:

Fix bugs and add small improvements.