move all version strings into org-install.el

move all version strings into org-install.el

	* targets.mk: check for release and git version and record this
	into environment variables for use in sub-make invocations; add
	new target "compile-dirty" that does not invoke "make clean" first
	* doc/Makefile, lisp/Makefile: remove git version check, since
	they are now provided by first-level make
	* lisp/Makefile: add insertion of version information into
	org-install.el, have org-install.el depend on LISPF rather than
	LISPC so that autoloads can be produced without compiling
	everything and remove insertion into org.el and re-compilation
	during install; add new target "compile-dirty" to support
	invocation from first-level make
	* lisp/org.el (org-version): remove determination of version
	information, show "N/A" if the information is not provided via
	org-install.el