Created README, basic build information.

Modified src/api functions to build without warnings, mostly unused
	variables that were declared.
Changed un/packstr into separate unpackstr_ptr and unpackstr_xmalloc,
	the first returns a pointer into the buffer, the second allocates
	memory and copies the string into it.
Converted integers in various job/node/partition structures into
	uint32_t for ease of passing across network with API.