Miscellaneous updates

[arango]

Several updates:

• Updated the weak constraint 4DVAR driver w4dvar_ocean.h to save the representer solution at the beginning of each outer loop.
• Created new subroutine checkadj.F to check for unsupported CPP options in adjoint-based algorithms. The execution will stop when such options are activated.
• Renamed file find_string.F to string.F. The new file is a module with several functions to manipulate strings. Currently, we have:

       find_string:  Scans a character array for a specified string
       lowercase:    Converts input string characters to lowercase
       uppercase:    Converts input string characters to uppercase
  

• Corrected several bugs in congrad.F. We were using module variables outer, inner and Ninner as arguments. This was in conflict the USE mod_scalars variable association. They were renamed to outLoop, innLoop and NinnLoop, repectively.
• Corrected several bugs in the representer model. Many thanks to Andy Moore for his help in finding and correcting these bugs.