PAM code cleanup & refactor

Divided functionality into classes, fixed comments +
various other cleanup. BackenAuth no longer increments
sequence on sending password. SQLite busy timeout shortened
to 1 second.

cmake/FindPAM.cmake

@@ -0,0 +1,19 @@
+# This CMake-file locates PAM libraries on the system
+#
+# The following variables are set:
+# PAM_FOUND - If the PAM library was found
+# PAM_LIBRARIES - Path to the library
+# PAM_INCLUDE_DIR - Path to headers
+
+find_path(PAM_INCLUDE_DIR pam_appl.h PATH_SUFFIXES security)
+find_library(PAM_LIBRARIES NAMES pam)
+message(STATUS "Found PAM include dirs: ${PAM_INCLUDE_DIR}")
+if (PAM_INCLUDE_DIR AND PAM_LIBRARIES)
+  message(STATUS "Found PAM: ${PAM_LIBRARIES}")
+  set(PAM_FOUND TRUE BOOL)
+else()
+  message(STATUS "PAM libraries not found")
+  set(PAM_FOUND FALSE BOOL)
+endif()
+
+