deploy: Rework kernel arguments, add --karg-append to "admin deploy"

The "ordered hash" code was really just for kernel arguments.  And it
turns out it needs to be a multihash (for e.g. multiple console=
arguments).

So turn the OstreeOrderedHash into OstreeKernelArgs, and move the bits
to split key=value and such into there.

Now we're not making this public API yet - the public OstreeSysroot
just takes char **kargs.  To facilitate code reuse between ostree/ and
libostree/, make it a noinst libtool library.  It'll be duplicated in
the binary and library, but that's OK for now.  We can investigate
making OstreeKernelArgs public later.

https://bugzilla.gnome.org/show_bug.cgi?id=721136

src/libostree/ostree-sysroot-private.h

@@ -21,7 +21,7 @@
 #pragma once
 
 #include "ostree.h"
-#include "ostree-ordered-hash.h"
+#include "ostree-kernel-args.h"
 #include "ostree-bootloader.h"
 
 G_BEGIN_DECLS
@@ -75,12 +75,6 @@ _ostree_sysroot_get_devino (GFile         *path,
 
 char *_ostree_sysroot_join_lines (GPtrArray  *lines);
 
-char *_ostree_sysroot_split_keyeq (char *str);
-
-OstreeOrderedHash *_ostree_sysroot_parse_kernel_args (const char *options);
-
-char * _ostree_sysroot_kernel_arg_string_serialize (OstreeOrderedHash *ohash);
-
 OstreeBootloader *_ostree_sysroot_query_bootloader (OstreeSysroot         *sysroot);
 
 G_END_DECLS