Changed const char* -> string in most of wpilibc.

The HAL will remain untouched in order to maintain C-style
compatibility. A few places in wpilibc were left as
C-style strings, especially if special formatting (eg,
elaborate uses of snprintf or sscanf) was being used.

In general, const char* was changed to std::string.
character buffers used for formatting were either
untouched, changed to std::stringstream, or changed
to std::string, depending on what was done with
the buffer.

Change-Id: I5e431ddf1cc4d9a6d534e1f21b16ea23be26e7f1

wpilibc/wpilibC++/src/Buttons/NetworkButton.cpp

@@ -8,12 +8,12 @@
 #include "Buttons/NetworkButton.h"
 #include "networktables/NetworkTable.h"
 
-NetworkButton::NetworkButton(const char *tableName, const char *field)
+NetworkButton::NetworkButton(const std::string &tableName, const std::string &field)
     :  // TODO how is this supposed to work???
       m_netTable(NetworkTable::GetTable(tableName)),
       m_field(field) {}
 
-NetworkButton::NetworkButton(::std::shared_ptr<ITable> table, const char *field)
+NetworkButton::NetworkButton(::std::shared_ptr<ITable> table, const std::string &field)
     : m_netTable(table), m_field(field) {}
 
 bool NetworkButton::Get() {