Big number code tidy and documentation update

Move the big number, big float and decimal fractions around to group them better

Clearly comment the deprecated functions

Improve documentation for big numbers, big floats and decimal fractions

Improve test coverage for big numbers a little

Optimize big number encoding



* big number and exp mantissa tidy up

* Big number documentation

* Fix commits of XCode project files

* documentation improvements

* Remove junk

---------

Co-authored-by: Laurence Lundblade <lgl@securitytheory.com>
diff --git a/QCBOR.xcodeproj/project.pbxproj b/QCBOR.xcodeproj/project.pbxproj
index cf51075..fbe0228 100644
--- a/QCBOR.xcodeproj/project.pbxproj
+++ b/QCBOR.xcodeproj/project.pbxproj
@@ -192,6 +192,7 @@
 		E7C960B82800A09E00FB537C /* ub-example.c */ = {isa = PBXFileReference; indentWidth = 3; lastKnownFileType = sourcecode.c.c; path = "ub-example.c"; sourceTree = "<group>"; tabWidth = 3; };
 		E7CA1F152C8ACCAE0008F454 /* qcbor_tag_decode.h */ = {isa = PBXFileReference; indentWidth = 3; lastKnownFileType = sourcecode.c.h; name = qcbor_tag_decode.h; path = inc/qcbor/qcbor_tag_decode.h; sourceTree = "<group>"; tabWidth = 3; };
 		E7CA1F1D2C8C337E0008F454 /* qcbor_tag_decode.c */ = {isa = PBXFileReference; fileEncoding = 4; indentWidth = 3; lastKnownFileType = sourcecode.c.c; name = qcbor_tag_decode.c; path = src/qcbor_tag_decode.c; sourceTree = "<group>"; tabWidth = 3; };
+		E7E305E02CE14447000E9348 /* Numbers.md */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = net.daringfireball.markdown; name = Numbers.md; path = doc/Numbers.md; sourceTree = "<group>"; };
 		E7FDBF16256C969D007138A8 /* QCBOR_Disable_Indef */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = QCBOR_Disable_Indef; sourceTree = BUILT_PRODUCTS_DIR; };
 		E7FDBF2C257A6C1F007138A8 /* QCBOR_Disable_Indef_array */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = QCBOR_Disable_Indef_array; sourceTree = BUILT_PRODUCTS_DIR; };
 /* End PBXFileReference section */
@@ -260,6 +261,7 @@
 			children = (
 				E776E161214EE19C00E67947 /* README.md */,
 				E743D132251014E60017899F /* Tagging.md */,
+				E7E305E02CE14447000E9348 /* Numbers.md */,
 				E7A7B60E2B76FB62009102C2 /* Serialization.md */,
 				E776E096214AE0C700E67947 /* cmd_line_main.c */,
 				E776E092214AE07C00E67947 /* inc */,