Modify the interface of Suurballe (#266, #181)

- Move the parameters s and t from the constructor to the run()
function. It makes the interface capable for multiple run(s,t,k)
calls (possible improvement in the future) and it is more similar
to Dijkstra.
- Simliarly init() and findFlow(k) were replaced by init(s) and
findFlow(t,k). The separation of parameters s and t is for the
future plans of supporting multiple targets with one source node.
For more information see #181.
- LEMON_ASSERT for the Length type (check if it is integer).
- Doc improvements.
- Rearrange query functions.
- Extend test file.

 SET(GLPK_REGKEY "[HKEY_LOCAL_MACHINE\\SOFTWARE\\GnuWin32\\Glpk;InstallPath]")

 GET_FILENAME_COMPONENT(GLPK_ROOT_PATH ${GLPK_REGKEY} ABSOLUTE)

 FIND_PATH(GLPK_INCLUDE_DIR

   glpk.h

   PATHS ${GLPK_REGKEY}/include)

 FIND_LIBRARY(GLPK_LIBRARY

   NAMES glpk

   PATHS ${GLPK_REGKEY}/lib)

 INCLUDE(FindPackageHandleStandardArgs)

 FIND_PACKAGE_HANDLE_STANDARD_ARGS(GLPK DEFAULT_MSG GLPK_LIBRARY GLPK_INCLUDE_DIR)

 IF(GLPK_FOUND)

   SET(GLPK_LIBRARIES ${GLPK_LIBRARY})

   SET(GLPK_BIN_DIR ${GLPK_ROOT_PATH}/bin)

 ENDIF(GLPK_FOUND)

 MARK_AS_ADVANCED(GLPK_LIBRARY GLPK_INCLUDE_DIR GLPK_BIN_DIR)